sfrank@orion.oac.uci.edu (Steven Frank) (10/31/90)
I need to buy a backup system in the 1-2 GB range for UNIX. I am
comparing DAT and Exabyte 8mm tape.
1. Any opinions on the merits and problems with each system
would be welcome.
2. Can anyone suggest articles of intermediate technical level that
describe how DAT and 8mm tape systems work and what the pratical
details are of using these systems (eg, seek times, etc)
3. What is the cost for medium for DAT drives?
steve frank
steve@fisher.bio.uci.edujhl@eecae.uucp (John Lawitzke) (10/31/90)
From article <272DB1E1.9737@orion.oac.uci.edu>, by sfrank@orion.oac.uci.edu (Steven Frank): $ I need to buy a backup system in the 1-2 GB range for UNIX. I am $ comparing DAT and Exabyte 8mm tape. $ $ 2. Can anyone suggest articles of intermediate technical level that $ describe how DAT and 8mm tape systems work and what the pratical $ details are of using these systems (eg, seek times, etc) For a good explanation of DAT, contact your local Archive distributor and ask for the Product Technical Manual for the Archive 4520. The 4520 is a SCSI DAT drive which is plug compatable with teh Archive 2150S. -- j |%|John Lawitzke, Dale Computer Corp., R&D |%|UUCP: uunet!mailrus!sharkey!dale1!jhl |%| or: uunet!frith!dale1!jhl Inquiring minds just wondering. |%|Internet: jhl@frith.egr.msu.edu
stevej@hpcpbla.HP.COM (Steve Jerman) (11/01/90)
>I Need To Buy A Backup System In The 1-2 Gb Range For Unix. I Am >Comparing Dat And Exabyte 8mm Tape. > >1. Any Opinions On The Merits And Problems With Each System > Would Be Welcome. Bearing in mind that I work for a DAT drive manufacturer, I've probably not got the most unbiased view in the world, but personally I think that DAT is the best thing since sliced bread (it that an American expression?). Howver I think I'll let users answer the question properly although email me if you've any specific questions and I'll answer them. >2. Can Anyone Suggest Articles Of Intermediate Technical Level That > Describe How Dat And 8mm Tape Systems Work And What The Pratical > Details Are Of Using These Systems (Eg, Seek Times, Etc) > On DAT there is an artical in IEEE Spectrum (Ocober 1989) which gives a good overview on the technology. Alternatively contact your local HP dealer and he should be able to give soome good info. >3. What Is The Cost For Medium For Dat Drives? > DDS media costs between $10 and $15 per cartridge. How about that for impartial! Steve Steve Jerman Hewlett Packard Computer Peripherals Bristol Address: Email: Filton Road stevej@hpcpbla.bri.hp.com Stoke Gifford Bristol BS12 6QZ UK Phone: Fax: (44) 272 799910 x22424 (44) 272 236091 **** Please note that the above views are mine and not ***** **** necessarily my employers *****
jparnas@larouch.uucp (Jacob Parnas) (11/05/90)
In article <9850004@hpcpbla.HP.COM>, stevej@hpcpbla.HP.COM (Steve Jerman) writes: |> >I Need To Buy A Backup System In The 1-2 Gb Range For Unix. I Am |> >Comparing Dat And Exabyte 8mm Tape. |> > |> >1. Any Opinions On The Merits And Problems With Each System |> > Would Be Welcome. At least for our uses, I think that the exabyte is definately a more useful drive. You get about double the capacity with the exabyte than the DAT, and that means half as much tape shuffling. The one advantage that the DAT drives have is faster access. We use the exabytes for backing up about 150 machines and we need about 2-3 restores per month, so the access time is much less important than the tape capacity. We back up 20-40 Gigabytes twice a month (one for off-site backup) and do incrementals. I think the 8mm tapes are also cheaper. They definately are cheaper per gigabyte. We've been really happy with our exabytes. We have 7 now and have 4 more on the way. They are cheap, fast, reliable and hold a mess o' data. ------------------------------------------------------------------------------ | Jacob M. Parnas | DISCLAIMER: The above message is from | | IBM Thomas J. Watson Research Ctr. | me and is not from my employer. IBM | | Arpanet: jparnas@ibm.com | might completely disagree with me. | | Bitnet: jparnas@yktvmx.bitnet \---------------------------------------| | Home: ..!uunet!bywater!acheron!larouch!jparnas | Phone: (914) 945-1635 | ------------------------------------------------------------------------------
kk881595@longs.LANCE.ColoState.EDU (kevin knappmiller) (11/06/90)
In article <272DB1E1.9737@orion.oac.uci.edu>, sfrank@orion.oac.uci.edu (Steven Frank) writes: > I need to buy a backup system in the 1-2 GB range for UNIX. I am > comparing DAT and Exabyte 8mm tape. > > 1. Any opinions on the merits and problems with each system > would be welcome. We have a Wang 1300 DAT, attached to a DECstation 5000 with a 600MByte Hard disk. When used for disk backups it works great. It is also good for the initial loading of software. The DDS format which this drive uses appears to have many capabilities which are not used by the typical UNIX software (ie. `tar'). We would really like to be able to use this tape drive as an extremely large floppy disk, for storage and file transfer. After reading the article in this month BYTE magazine, it appears that a formatting and sectoring of the tape (given access times of 60 seconds) is possible. This would be much preferable to using `tar'. Does anyone know of software which supports the entire set of DDS commands, and allows a more user friendly interface to the DAT tape? > > 2. Can anyone suggest articles of intermediate technical level that > describe how DAT and 8mm tape systems work and what the pratical > details are of using these systems (eg, seek times, etc) November BYTE magazine. > > 3. What is the cost for medium for DAT drives? ~$16 per 1.3 GByte tape (60m, 4mm) > > kevin knappmiller kk881595@longs.lance.colostate.edu Fort Collins, Colorado
kusumoto@chsun1.uchicago.edu (Bob Kusumoto) (11/06/90)
sfrank@orion.oac.uci.edu (Steven Frank) writes: >I need to buy a backup system in the 1-2 GB range for UNIX. I am >comparing DAT and Exabyte 8mm tape. >1. Any opinions on the merits and problems with each system > would be welcome. 8mm: double storage capacity of the DAT, with the media capable of handling at least 5GB if not more without compression. Slower than DAT for file recovery, costs more (exabyte is the only company that makes 8mm drives). Cheap tapes (commerical Sony 8mm tapes can run between $5 and $10, exabyte certified tapes run between $10 and $15). DAT: current storage capacity around 1.3GB and the media is pretty close to its capacity, but it's possible to expand it with compression (but then you get into the pros and cons of compression and data reliability). Tapes costs around $12, with the range betwenn $10 and $17. Recovery of a file is faster since it can reach the file more quickly than 8mm. Lots of companies sell DAT drives because the technology is connected to commerical audio markets (cost of R&D is lower on DAT than 8mm). >2. Can anyone suggest articles of intermediate technical level that > describe how DAT and 8mm tape systems work and what the pratical > details are of using these systems (eg, seek times, etc) The recent SunTech Journal I got (sept/oct) has a few articles talking about the ins and outs of 8mm and DAT technology. >3. What is the cost for medium for DAT drives? pricing for DAT drives is around $4k-$6k. Exabyte drives go for $6k-$7k although I've seen some people try and sell them for $9k and up. The question is what's important for you: storage capacity: 8mm wins hands down. The new exabyte 8500 holds 5GB of storage on an single 8mm tape (doubles the current throughput of the 8200 as well). fast recovery: DAT wins here. I think the commercial audio DAT tapes can go from one end to the other end of the tape in 38 seconds. Imagine how fast it can locate a file on a tape for you compared to a few minutes on the Exabyte. cost: the DAT drive costs less but the tapes cost more. If you look at the price of the tape per GB, the DAT tapes cost even more. Since the commerical Sony 8mm tapes are pretty cheap, and they can handle at least 2.3GB if not the newer 5GB format, they cost less per GB. Even the tapes certified to go 5GB when the 8500 is out from OEMs would be cheaper at $20 per tape per GB than DATs (at 5GB 8mm at $20 each, the cost is $4/GB, while a $10 DAT is $7.70/GB). the SunTech article also talks about the current debate and "war" over which compression technology is being used in DAT drive to increase their capacity, but you also have to weigh how much more important capacity is worth to you over data integrety after uncompression. Bob Bob Kusumoto | Find the electric messiah! Internet: kusumoto@chsun1.uchicago.edu | The AC/DC God! Bitnet: kusumoto@chsun1.uchicago.bitnet | - My Life with the Thrill Kill UUCP: ...!{oddjob,gargoyle}!chsun1!kusumoto | Kult, "Kooler than Jesus"
tim@gumby.cs.caltech.edu (Timothy L. Kay) (11/06/90)
Bob Kusumoto's comments are marked by >> Steven Frank's comments are marked by > >8mm: double storage capacity of the DAT, with the media capable of handling >at least 5GB if not more without compression. Slower than DAT for file >recovery, costs more (exabyte is the only company that makes 8mm drives). This is true of the EXB8200 but not of the EXB8200-SX and the EXB8500. The latter two drives (soon to be available) are faster at seeking than the DAT drives. >>3. What is the cost for medium for DAT drives? >pricing for DAT drives is around $4k-$6k. Exabyte drives go for $6k-$7k >although I've seen some people try and sell them for $9k and up. I can tell you where to get an Exabyte drive for $2500. Tim
wcarroll@encore.com (Mr. New Dad) (11/08/90)
From article <kusumoto.657844687@chsun1>, by kusumoto@chsun1.uchicago.edu (Bob Kusumoto): > 8mm: > Cheap tapes (commerical Sony 8mm tapes can run between $5 and $10, exabyte > certified tapes run between $10 and $15). Note: Exabyte tapes ARE Sony tapes. Exabyte buys them from Sony and repackages them. I don't recall whether the Exabyte tapes are screened in any way to improve data reliability. > > DAT: > Lots of companies > sell DAT drives because the technology is connected to commerical audio > markets (cost of R&D is lower on DAT than 8mm). I don't buy this. I'd wager that a whole lot more 8mm video units have been sold than audio DAT drives. The interface to the DAT unit may be easier than with 8mm, but the economies of scale for the drive/head assembly favor 8mm, not DAT. -- William R. Carroll (Encore Computer Corp., Ft. Lauderdale FL) wcarroll@encore.com uunet!gould!wcarroll "The brain-dead should not be allowed to operate motor vehicles!" - Me
sfrank@orion.oac.uci.edu (Steven Frank) (11/08/90)
Several people requested a summary of the 8mm versus Tape debate:
1. All 8mm units are currently made by Exabyte, although other
manufacturers package the drive. The current model that is
available is the EXB8200, which holds 2.3 GB per tape. Each
tape costs about $7. This model is available from anDATAco
for $2400. Call (800) 334-9191.
2. The 8mm EXB8200 has a very slow seek time. A new model available
next month, EXB8200-SX will have a seek time comparable to DATs
(so they say). The new drive has a chip that counts servo pulses.
How well it works in practice is not known (eg, drivers, etc).
The new model is about $3000. Finally, a EXB8500 will be out
soon that has fast seek and holds 5 GB per tape.
3. People using the Exabytes are uniformly pleased with performance, etc,
but of course do not use the machines for anything other than dumps
since the seek times are slow. Also, the drives apparently need
to be cleaned about every 30 hours of use, and cleaning does
affect performance.
4. Many people are very enthusiastic about DATs. Since DATs are new
not surprisingly most responses are from people associated with
manufacturers. Some facts: (a) current DATs hold 1.3 GB per tape;
(b) seek times are relatively fast, 20-40 seconds for any file
on a tape.
5. Some articles about DATs: (a) IEEE Spectrum, Oct 1989, (b) Nov Byte;
(c) SunTech journal ??
6. Some advantages claimed for DATs relative to 8mm: (a) DAT is digital
whereas 8mm is an analogue medium (why this is a big advantage isn't
clear, beyond obvious fact that data from hard disks are digital);
(b) DATs are cheaper; (c) DATs are self-cleaning; (d) DATs are the
tape drive of the future, so prices will continue to drop; (e) fast
seek is easier to implement for DATs because of the mechanics of
read/write and storage; (f) DATs have enthusiasm of many vendors.
(g) future DATs will have higher capacities than 8mm..
7. My current impression of the claimed advantages in 6:
(a) I don't know???
(b) I have prices only for Hewlett-Packard DATs (street prices).
The 35450-67905 is $1925 from Lex Electronics (714) 587-0404.
(c) Seems to be true
(d) Hard to judge. Many manufacturers are selling or developing
DATs. Apparently they can and will soon be made in 3.5" form
factor, and will be pushed in the PC and MAC market. Acceptance
in these markets guarantees lower prices, more competition
and more variation in product quality, with the best being
very good.
(e) Appears to be true, although new Exabytes are said to be just
as fast although more expensive.
(f) True
(g) HP has announced a 2 GB 3.5" DAT (35470) and a similar drive
with hardware compression (8 GB with compression). 8mm is
near releasing 5 GB drives. My guess is that DATs may be
behind here, but price per GB may soon favor DATs. (The new
HP drives will not be available for 6 to 9 months).
8. Overall, it is a toss-up at present. The future does seem to favor
DATs, but that is hard to predict.
9. REQUEST: Please send model numbers, street prices and vendor names and
phone numbers for DAT drives. Many claim that DATs are cheaper, but
actual prices and vendors are needed by those of us considering a
purchase.
Thanks,
steve frank
steve@fisher.bio.uci.edu sfrank@orion.oac.uci.edu (Steven Frank) (11/08/90)
In article <27388281.13536@orion.oac.uci.edu> steve@fisher.bio.uci.edu (Steven Frank) writes: >Several people requested a summary of the 8mm versus Tape debate: ^^^^ OOPS: 8mm Tape versus DAT debate!
peterk@hpcpbla.HP.COM (Peter King) (11/08/90)
A Few Thoughts On Your DAT vs 8mm Choice
========================================
I thought I would add to the current debate with a few pointers:
* You may be interested to know that HP has just announced 2 new DAT
drives:
- A low cost drive with 2 GByte capacity, and
- A high performance drive, with built-in Data Compression with
capacity of up to 8 GBytes.
- Both drives have a 3.5" Half Height Form Factor.
The drives will be demonstrated at Comdex next week and should be
shipping in volume by mid-91.
Both drives will support 90m DAT cassettes to increase capacity beyond
the current 1.3 GBytes (60m tape). The high performance drive uses
hardware data compression to enhance performance and capacity. Expect
to see a compression ratio in the range 2 to 4 (Typically around 2.5
on most UN*X systems) giving a maximum capacity of 8 GBytes and a maximum
transferrate of 732 KBytes/s. (>2.5 GBytes/hour!).
All in a 3.5" package.
* Industry Analysts predict a bright future for DAT. The leading analysts
seem to agree that:
DAT shipments are expected to outstrip 8mm shipments during 1991 for
the first time - with DAT forecast shipments running at around 150,000
units during 1991 (up on around 60,000 in 1990).
Forecasts show DAT shipments running at around 1/2 million per year by
1994 - more than double the 8mm forecast of around 200,000 units.
* Industry Analysts also predict that DAT is likely to be far cheaper than
8mm - partly the result of DAT's 3.5" form factor.
* The DDS Standards activity is also likely to play a major part in DAT's
success.
The DDS Standard has now been adopted as an ECMA Standard and is
anticipated to become an ANSI Standard in the first haly of 1991.
There are now 18 companies participating in the DDS Manufacturers Group
- including Exabyte and most of the major Quarter Inch Cartridge
manufacturers.
* There are also hundreds of different DAT solutions. DAT is supported on
systems from HP and DEC - with third party support on Sun systems, IBM PC
compatibles, SCO Un*x, Novell etc. The list goes on!
* Check-out Digital Review's recent article (June 90). They look at the
issue of 8mm performance and capacity. Their results are interesting.
They show that 8mm capacity and transfer rate are significantly reduced
when short saveset sizes are used. For example:
Saveset Size 8mm Capacity
25 MBytes 2 GBytes
5 MBytes 1.4 GBytes
1 MBytes 560 MBytes
And they also conclude that for savesets of less than 125 MBytes DAT
Transfer Rate is faster than 8mm.
Performance and capacity are not simple "scalar" quantities - they depend
significantly upon the application as DR's review shows.
I hope this information helps you make your choice. 8mm was clearly first
to market but the future looks really bright for DAT.
Regards,
Peter King.chris@com50.c2s.mn.org (Chris Johnson) (11/09/90)
In article <129505@jake.encore.com> wcarroll@encore.com (Mr. New Dad) writes: >From article <kusumoto.657844687@chsun1>, by kusumoto@chsun1.uchicago.edu (Bob Kusumoto): >> DAT: >> Lots of companies >> sell DAT drives because the technology is connected to commerical audio >> markets (cost of R&D is lower on DAT than 8mm). > >I don't buy this. I'd wager that a whole lot more 8mm video units have >been sold than audio DAT drives. The interface to the DAT unit may be >easier than with 8mm, but the economies of scale for the drive/head >assembly favor 8mm, not DAT. >-- >William R. Carroll (Encore Computer Corp., Ft. Lauderdale FL) In fact, you're exactly correct, Mr. Carroll. Blank DAT tapes cost _more_ than blank 8mm Video tapes, as do the drive components, presently. Volume manufacturing, and even better, competing manufacturers, generally tend to lower the prices. Right now, things are kind of backwards. 8mm mechanisms are only made by one company, but lots of companies make media. A lot fewer units of DAT are being made, but at least, there are more than one mechanism producer. Relative prices will change, soon, I suspect. -- ...Chris Johnson chris@c2s.mn.org ..uunet!bungia!com50!chris Com Squared Systems, Inc. St. Paul, MN USA +1 612 452 9522
mcconnel@b11.ingr.com (Guy McConnell) (11/09/90)
In article <129505@jake.encore.com>, wcarroll@encore.com (Mr. New Dad) writes: > From article <kusumoto.657844687@chsun1>, by kusumoto@chsun1.uchicago.edu (Bob Kusumoto): > > 8mm: > > Cheap tapes (commerical Sony 8mm tapes can run between $5 and $10, exabyte > > certified tapes run between $10 and $15). > > Note: Exabyte tapes ARE Sony tapes. Exabyte buys them from Sony and > repackages them. I don't recall whether the Exabyte tapes are screened > in any way to improve data reliability. Um, Sony makes AND packages the tapes for Exabyte. The Exatapes carry the "D8" trademark to indicate that they are certified for data storage, just as Sony DAT tapes carry their "DDS" trademark for the same reason. > > Lots of companies > > sell DAT drives because the technology is connected to commerical audio > > markets (cost of R&D is lower on DAT than 8mm). > > I don't buy this. I'd wager that a whole lot more 8mm video units have > been sold than audio DAT drives. The interface to the DAT unit may be > easier than with 8mm, but the economies of scale for the drive/head > assembly favor 8mm, not DAT. The development cost difference is due to the fact that Exabyte owns so many patents on the 8mm data storage format and silicon. They also have an exclusive marketing arrangement with Sony in which they (and their Pacific Rim partner, Kubota) are the only ones who can purchase the modified Sony decks. It would cost a bundle to develop an 8mm drive because a company would either have to buy the technology from Exabyte or spend big time and money developing a system from the ground up (as Exabyte did). DAT is a consumer technology and the majority of its components can be bought off the shelf, sans interface and code. Exabyte holds a license to the DDS format and were originally developing a 4mm drive. They went to 8mm because they felt that they could ultimately do more with it. -- ============================================================================ Guy D. McConnell | | "I'd like to be Intergraph Corp. Huntsville, AL. | Opinions expressed | under the sea Mass Storage Peripheral Evaluation | are mine and do not | In an octopus' Tape Products | necessarily reflect | garden in the uunet!ingr!b11!mspe5!guy | Intergraph's. | shade..." (205)730-6289 FAX (205)730-6011 | | --The Beatles-- ============================================================================
mcconnel@b11.ingr.com (Guy McConnell) (11/09/90)
In article <27388281.13536@orion.oac.uci.edu>, sfrank@orion.oac.uci.edu (Steven Frank) writes: > Several people requested a summary of the 8mm versus Tape debate: > > 1. All 8mm units are currently made by Exabyte, although other > manufacturers package the drive. The current model that is > available is the EXB8200, which holds 2.3 GB per tape. Each > tape costs about $7. This model is available from anDATAco > for $2400. Call (800) 334-9191. Kubota of Japan also manufactures these drives and sells them in the Pacific Rim. All U.S. destined units made at Kubota still go through the Exabyte facility in Boulder for read/write compatibility testing, quality control, etc. The current product spec states that the drive (with the 112m Exatape) will hold 2.5 Gb per tape. I can easily get 2.1 to 2.3 Gb per tape EVERY time, now matter what you have been told. > 2. The 8mm EXB8200 has a very slow seek time. A new model available > next month, EXB8200-SX will have a seek time comparable to DATs > (so they say). The new drive has a chip that counts servo pulses. > How well it works in practice is not known (eg, drivers, etc). > The new model is about $3000. Finally, a EXB8500 will be out > soon that has fast seek and holds 5 GB per tape. The EXB-8500 has a faster seek time than DAT. > 3. People using the Exabytes are uniformly pleased with performance, etc, > but of course do not use the machines for anything other than dumps > since the seek times are slow. Also, the drives apparently need > to be cleaned about every 30 hours of use, and cleaning does > affect performance. I am very pleased with the Exabyte drive and I use it for backups, restore operations, data exchange, etc. The drives do need cleaning every 30 Gb or monthly, whichever comes first. The cleaning cartridge will not cause head wear and therefore will not affect performance. Not cleaning the heads will degrade performance on the Exabyte as well as any other tape drive (including DAT!). > 6. Some advantages claimed for DATs relative to 8mm: (a) DAT is digital > whereas 8mm is an analogue medium (why this is a big advantage isn't > clear, beyond obvious fact that data from hard disks are digital); > (b) DATs are cheaper; (c) DATs are self-cleaning; (d) DATs are the > tape drive of the future, so prices will continue to drop; (e) fast > seek is easier to implement for DATs because of the mechanics of > read/write and storage; (f) DATs have enthusiasm of many vendors. > (g) future DATs will have higher capacities than 8mm.. > > 7. My current impression of the claimed advantages in 6: > (a) I don't know??? Ask someone from the DAT camp to attach a scope or analyzer to the output of the head and show you the "digital" signal. What? It's analog too? Well, imagine that. All magnetic recordings are analog, including hard disks. > (c) Seems to be true Someone is pulling your chain. They are NOT self-cleaning. There are DAT cleaning cartridges to use for this purpose. They look just like regular DAT tape because they are an abrasive chromium dioxide formulation, just like consumer 8mm video cleaning cartridges. Go to the video store and read the fine print on the cleaning cartridge. It says "Do not use cleaning cartridge excessively as premature head wear will result". That is why Exabyte uses a specially developed cloth cleaning cartridge and use of a video cleaning cartridge will void their warranty. > (d) Hard to judge. Many manufacturers are selling or developing > DATs. Apparently they can and will soon be made in 3.5" form > factor, and will be pushed in the PC and MAC market. Acceptance > in these markets guarantees lower prices, more competition > and more variation in product quality, with the best being > very good. There is currently one manufacturer shipping 3.5" DAT drives (I have one in my lab). There is a shakeout going on in the DAT market after which only the "major players" will be left. > (e) Appears to be true, although new Exabytes are said to be just > as fast although more expensive. Fast search is just as difficult to implement on one as the other from a software standpoint. > (f) True > (g) HP has announced a 2 GB 3.5" DAT (35470) and a similar drive > with hardware compression (8 GB with compression). 8mm is > near releasing 5 GB drives. My guess is that DATs may be > behind here, but price per GB may soon favor DATs. (The new > HP drives will not be available for 6 to 9 months). Most or all of the DAT vendors are working on a 3.5" drive. Only one is shipping them now but it isn't HP. Bear in mind that the same type of media is used in both 8mm and 4mm and that anything that can be done to increase capacity on DAT (i.e. compression and longer tape) can be done on 8mm as well. The converse is not true. DAT is close to maximum areal density with current technology at 114 Mb/sq. in. and therefore cannot easily (possibly?) increase capacities by increasing track density. Current 8mm tape is at 35 Mb/sq. in. and the new 5 Gb drive will have and areal density of 74.4 Mb/sq.in. This gives a path to double capacity once more after this WITHOUT data dependent compression algorithms. > 8. Overall, it is a toss-up at present. The future does seem to favor > DATs, but that is hard to predict. Both have their strong points but, until quite recently, all of DAT's claims and selling points were on paper only and not field proven. They are only now begining to ship in sufficient volumes to verify or nullify their specs. Stay tuned. -- ============================================================================ Guy D. McConnell | | "I'd like to be Intergraph Corp. Huntsville, AL. | Opinions expressed | under the sea Mass Storage Peripheral Evaluation | are mine and do not | In an octopus' Tape Products | necessarily reflect | garden in the uunet!ingr!b11!mspe5!guy | Intergraph's. | shade..." (205)730-6289 FAX (205)730-6011 | | --The Beatles-- ============================================================================
rayan@cs.toronto.edu (Rayan Zachariassen) (11/09/90)
Are there any computer-DAT drives that can be used as audio-DAT drives (i.e., with a digital- or analog-out connector somewhere to hook up to other parts of a stereo system). Some people here were interested in DAT iff that combination exists (for their research needs!), but it is interesting to ponder the possibilities... rayan
iwelch@agsm.ucla.edu (Ivo Welch) (11/09/90)
I have heard rumors that DAT drives are not very reliable, i.e. the head assembly goes after a small number of hours used. Is this true? Is there a random-access way to access either DAT or 8mm drives as a big floppy? Occasionally, I would like to store large databases (800MB) consisting of many individual files that would mainly be accessed sequentially. I don't care very much for the Unix dump/restore handling in the first place. Copying a few files directly to another disk device would make things much simpler. What are currently the cheapest sources and quickest availability for academics of the new fast-access 8mm and DAT drives? Can I hook one of these up to any SCSI interface, and plug and go, or do I have to know stuff about hardware and interface software below dump/restore? /ivo welch ivo@next.agsm.ucla.edu
kev@hpcpbla.HP.COM (Kevin Jones) (11/09/90)
> The EXB-8500 has a faster seek time than DAT. My understanding is that the EXB-8500 achieves a fast "seek" by the following process: 1. Host writes data to the drive 2. During the write operation (or a subsequent read pass at normal speed), the host may as the drive to report current physical tape position (as a count of servo pulses). 3. When a "seek" to a specific record is required, the host can command the drive to "position to XX servo pulses from start of tape". This is not a seek function. It is a goto function. I have no doubts that it can prove just as effective as DAT seeks, PROVIDING the servo pulse count information (call it INDEXING information) is readily available whenever a fast "seek" is required. In order to utilise this ability you will need * A driver cabable of "gathering" indexing information as it writes. * A driver cabable of preserving ?somewhere? this information until it is needed. * A driver capable of reading and associating this information with some requested logical position, then issuing the appropriate command to the drive to "get there". - ie. A highly Exabyte specific custom driver. I would like to point out that DDS-DAT implements a GENUINE fast search. DDS drives maintain counts of "records so far", "filemarks so far" and "setmarks so far" which they embedd in the data as it is written to tape. These counts can be read by the drive as it seeks at up to 200X normal speed. Any host driver capable of issuing a SCSI 'SPACE' command (STANDARD SCSI) can therefore reap the benefits of DDS fast search. DATA COMPRESSION: > but then you get into the pros and > cons of compression and data reliability There are no pro's and cons of data integrity / error rate / reliability with the data compression being used on HP's (and other) DDS drives. HP drives (DC and non DC) both have error rates of LESS THAN 1 BIT IN EVERY 10^15 BITS UNCORRECTABLE. Data integrity is not compromised by the addition of DC. The adaptive DC algorithms being used mean that the argument "trash your dictionary and you trash your tape" no longer holds. Adaptive DC algorithms reset their dictionaries repetitively. The argument "with 4X compression, loosing 1 bit on tape means you loose 4 bits at the host" does apply, but bear in mind that with data compression, LESS DATA ON TAPE is used to store the SAME AMOUNT OF HOST DATA. A given quantity "N" of host data is therefore "X" times LESS likely to suffer from an uncorrectable error. If an uncorrectable error does occur however, then instead of 1 bit in error, you've got "X" bits in error. The net result is that the error rate is unchanged. (This analysis is a bit simplified, the nature of ECC schemes used in drives means you don't go loosing individual BITS. Instead, you typically fail to correct a BLOCK. The truth is, that with DDS's 1 in 10^15 error rate, you are more likely to loose data thru misuse of tape/drives than due to the "natural" error rate of the drive. eg. store tapes in high humidity, store tapes on top of your non-magnetically screened display, use tapes beyond their specified life, fail to adhere to reccomended maintenance practices such as head cleaning ......) Another attempt at an unbiased opinion from a DDS develpment engineer............... ----------------------------------------------------------------- Kevin Jones. (in DATland) | Hewlett Packard Ltd, | Computer Peripherals Bristol, kev%hpcpbla@hplb.hpl.hp.com | Filton Road, | Stoke Gifford, Tel: 011 44 272 799910 (ext 22351) | Bristol. BS12 6QZ. | ENGLAND. ----------------------------------------------------------------- This response does not represent the official position of, or statement by, the Hewlett-Packard Company. The above data is provided for informational purposes only. It is supplied without warranty of any kind.
hashemi@leadsv.UUCP (Rahmat O. Hashemi) (11/10/90)
In article <9850005@hpcpbla.HP.COM> peterk@hpcpbla.HP.COM (Peter King) writes:
+ A Few Thoughts On Your DAT vs 8mm Choice
+ ========================================
+
+I thought I would add to the current debate with a few pointers:
+
+* You may be interested to know that HP has just announced 2 new DAT
+ drives:
+
+ - A low cost drive with 2 GByte capacity, and
+ - A high performance drive, with built-in Data Compression with
+ capacity of up to 8 GBytes.
+ - Both drives have a 3.5" Half Height Form Factor.
+
+ The drives will be demonstrated at Comdex next week and should be
+ shipping in volume by mid-91.
+
+ Both drives will support 90m DAT cassettes to increase capacity beyond
+ the current 1.3 GBytes (60m tape). The high performance drive uses
+ hardware data compression to enhance performance and capacity. Expect
+ to see a compression ratio in the range 2 to 4 (Typically around 2.5
+ on most UN*X systems) giving a maximum capacity of 8 GBytes and a maximum
+ transferrate of 732 KBytes/s. (>2.5 GBytes/hour!).
+
+ All in a 3.5" package.
I saw this article(someone had left it on my desk) from some magazine(the
article was cut out, so I couldn't see what magazine it was from).
Since I am in the market for some tape generation equipment, I called HP
to get some info. on these products(only 3 days ago). They told me that the
article was written by someone who had misheard the facts, and the product is
not really a product yet, and no specs are available now. The product may be
shipable by the end of 91/early 92, and it will be an OEM product. So if you
have a need right now, don't go holding your breath for the HP product.
+
+* Industry Analysts predict a bright future for DAT. The leading analysts
+ seem to agree that:
+
+ DAT shipments are expected to outstrip 8mm shipments during 1991 for
+ the first time - with DAT forecast shipments running at around 150,000
+ units during 1991 (up on around 60,000 in 1990).
+
+ Forecasts show DAT shipments running at around 1/2 million per year by
+ 1994 - more than double the 8mm forecast of around 200,000 units.
+
+* Industry Analysts also predict that DAT is likely to be far cheaper than
+ 8mm - partly the result of DAT's 3.5" form factor.
+
+* The DDS Standards activity is also likely to play a major part in DAT's
+ success.
+
+ The DDS Standard has now been adopted as an ECMA Standard and is
+ anticipated to become an ANSI Standard in the first haly of 1991.
+
+ There are now 18 companies participating in the DDS Manufacturers Group
+ - including Exabyte and most of the major Quarter Inch Cartridge
+ manufacturers.
+
+* There are also hundreds of different DAT solutions. DAT is supported on
+ systems from HP and DEC - with third party support on Sun systems, IBM PC
+ compatibles, SCO Un*x, Novell etc. The list goes on!
+
+* Check-out Digital Review's recent article (June 90). They look at the
+ issue of 8mm performance and capacity. Their results are interesting.
+ They show that 8mm capacity and transfer rate are significantly reduced
+ when short saveset sizes are used. For example:
+
+ Saveset Size 8mm Capacity
+
+ 25 MBytes 2 GBytes
+ 5 MBytes 1.4 GBytes
+ 1 MBytes 560 MBytes
+
+ And they also conclude that for savesets of less than 125 MBytes DAT
+ Transfer Rate is faster than 8mm.
+
+ Performance and capacity are not simple "scalar" quantities - they depend
+ significantly upon the application as DR's review shows.
+
+I hope this information helps you make your choice. 8mm was clearly first
+to market but the future looks really bright for DAT.
+
+Regards,
+
+Peter King.tim@gumby.cs.caltech.edu (Timothy L. Kay) (11/10/90)
I just thought I'd point out that comments coming from Peter King, a Hewlett-Packard employee, are a bit biased. While such opinions are not unexpected nor unwelcomed, people who are obviously biased and comercially oriented should exercise some restraint when making comments. A nice example of such restraint is demonstrated by the people at FTP Software in the groups comp.protocols.tcp-ip. Whenever they present a feature of their software, they always give a *fair* representation of the competition. Instead, Mr. King has chosen to present HP's marketting hype. peterk@hpcpbla.HP.COM (Peter King) writes: > Both drives will support 90m DAT cassettes to increase capacity beyond > the current 1.3 GBytes (60m tape). The high performance drive uses > hardware data compression to enhance performance and capacity. Expect > to see a compression ratio in the range 2 to 4 (Typically around 2.5 > on most UN*X systems) giving a maximum capacity of 8 GBytes and a maximum > transferrate of 732 KBytes/s. (>2.5 GBytes/hour!). Wow! And if I can compress my data eight times, then I'll get a transfer rate of 1464 KB/s and a capacity of 16 GB. And if I compress my data 16 times, then I'll get a transfer rate of 2928 KB/s and a capacity of 32 GB! Zow! Unfortunately I need all the capacity I can get. I already compress my data before I put it on an Exabyte tape drive. No amount of marketing double speak is going to change the fact that the HP drive holds *two* GB data. And just how much do those extended length tapes cost? I can get an 8mm 2.3 GB tape for the Exabyte for $4.75 now, quantity one, at the store down the street. > All in a 3.5" package. And when can I get one of those drives? Maybe a year from now? And how much is it going to cost me? Remember we are talking HP pricing. Sheesh, I'm surprised the DAT drives don't have HPIB interfaces on them. I'd be willing to bet that Exabyte will produce a 3.5" form factor drive. Perhaps we'll see one before the HP drives become available. >* Industry Analysts predict a bright future for DAT. The leading analysts > seem to agree that: Have anaylysts factored in the fact that disk drives are getting *very* cheap? Very soon, 2 GB of data will be small potatoes. Many Novell networks now have well over a GB of data already. In a year, they'll have to throw out their HP drive and get something that solves their problem. I don't have much confidence in industry analysts. > DAT shipments are expected to outstrip 8mm shipments during 1991 for > the first time - with DAT forecast shipments running at around 150,000 > units during 1991 (up on around 60,000 in 1990). > Forecasts show DAT shipments running at around 1/2 million per year by > 1994 - more than double the 8mm forecast of around 200,000 units. That doesn't mean that I want one. I want the best solution, not the solution that is popular just because there is a big company behind it. (For the same reason, I would never buy an HP workstation.) >* Industry Analysts also predict that DAT is likely to be far cheaper than > 8mm - partly the result of DAT's 3.5" form factor. Smaller is cheaper? In what way? 3.5" disk drives are more expensive than 5.25" disk drives, after all. This includes both hard and floppy drives. Same for the diskettes. Small audio tape players cost more than the normal-sized ones. >* Check-out Digital Review's recent article (June 90). They look at the > issue of 8mm performance and capacity. Their results are interesting. > They show that 8mm capacity and transfer rate are significantly reduced > when short saveset sizes are used. For example: > Saveset Size 8mm Capacity > 25 MBytes 2 GBytes > 5 MBytes 1.4 GBytes > 1 MBytes 560 MBytes > And they also conclude that for savesets of less than 125 MBytes DAT > Transfer Rate is faster than 8mm. And how many people use datasets of 1 MB? You'd be better off with floppy disks. I put a tape in, I back up my system, and I am done. If I had to use a DAT, it wouldn't fit, and I'd have to come back in the middle of the night. How many statistics do I need to look at to determine which drive is right for me? Tim
kusumoto@chsun1.uchicago.edu (Bob Kusumoto) (11/11/90)
iwelch@agsm.ucla.edu (Ivo Welch) writes: >Is there a random-access way to access either DAT or 8mm drives as a big >floppy? Occasionally, I would like to store large databases (800MB) consisting >of many individual files that would mainly be accessed sequentially. I don't >care very much for the Unix dump/restore handling in the first place. Copying >a few files directly to another disk device would make things much simpler. It's possible to do something like this. If you use the dd command and treat the tape drive like a 9-track tape, you might be able to do something that you want to get out of it. >What are currently the cheapest sources and quickest availability for >academics of the new fast-access 8mm and DAT drives? Can I hook one of these >up to any SCSI interface, and plug and go, or do I have to know stuff about >hardware and interface software below dump/restore? You'll have to go through channels to get them, Exabyte is the only manufacturer of 8mm tape drives. I hear from the Novell mailing list that Mountain and Maynard are the DAT drives of choice. whether you can plug them onto your SCSI bus and go depends on how the kernal handles tape drives and whether it can handle something that large (for sparcstations, you need either a patched SunOS 4.0.3 or use SunOS 4.1.1 for the tape drive to work, plus make sure the SCSI address on the drive is ok. SunOS kernals usually are set up for 4 hard drives and 2 tape drives). Bob Bob Kusumoto | Find the electric messiah! Internet: kusumoto@chsun1.uchicago.edu | The AC/DC God! Bitnet: kusumoto@chsun1.uchicago.bitnet | - My Life with the Thrill Kill UUCP: ...!{oddjob,gargoyle}!chsun1!kusumoto | Kult, "Kooler than Jesus"
pavlov@canisius.UUCP (Greg Pavlov) (11/15/90)
In article <9850005@hpcpbla.HP.COM>, peterk@hpcpbla.HP.COM (Peter King) writes: > > A Few Thoughts On Your DAT vs 8mm Choice > ======================================== > > * There are also hundreds of different DAT solutions. DAT is supported on > systems from HP and DEC - > Note that DEC announced a DAT drive (manufactured by HP ?) many months ago but has never shipped. It has been selling 8mm drives as a substitute. In all of the "pros and cons" articles that I have seen "comparing" 4mm DAT to 8mm, there is very little to differentiate the two in terms of the prim- ary application of the devices, which is backup. Since most of the arguments appear to be put forth either by manufacturers/ resellers of the devices or in a few cases are simply rumor-mongering (the "analog" vs "digital" disinformation being the primary example), I have to throw in my own unsubstantiated prejudice: it is true that both technologies will permit very considerable storage per unit (e.g., a cartridge). But I have to be concerned with long-term storage as well as short-term backups. I have some doubt about the long-term viability of the data stored on either of these formats. But since I do, I would rather bet on the lower density of the 8mm medium, when considering two units of the same capacity. greg pavlov, fstrf, amherst, ny pavlov@stewart.fstrf.org
ghg@en.ecn.purdue.edu (George Goble) (11/15/90)
In article <3007@canisius.UUCP> pavlov@canisius.UUCP (Greg Pavlov) writes: > I have some doubt about the long-term viability of the data stored on either > of these formats. But since I do, I would rather bet on the lower density > of the 8mm medium, when considering two units of the same capacity. > > greg pavlov, fstrf, amherst, ny > pavlov@stewart.fstrf.org I can still read the 8mm tapes made during the summer of 1987 made on the engineering prototypes of the EXB-8200. Studies have shown that 8mm holds magnetization better than 1/2" magtape. They are very hard to erase, "refrigerator" and other "normal" magnets will not hurt them and neither will cheap "audio" erasers. Strong alnico (speaker magnets) and the radio shaft high power video eraser will erase them though. Try this (normal magnets) on 1/2" magtape sometime. > --ghg
tim@gumby.cs.caltech.edu (Timothy L. Kay) (11/16/90)
pavlov@canisius.UUCP (Greg Pavlov) writes: > I have some doubt about the long-term viability of the data stored on either > of these formats. But since I do, I would rather bet on the lower density > of the 8mm medium, when considering two units of the same capacity. Exabyte is claiming that the data should be readable for at least ten years if you use their tapes. (Their tapes cost $40 each! I'd rather use the $4.75 variety and take my chances.) Tim
seals@uncecs.edu (Larry W. Seals) (11/16/90)
As to taking your chances with non-Exabyte tapes:
We received several recommendations from other sites on our choice of
8mm tapes to use instead of Exabyte (we objected to the price too).
The general opinion favored Sony P6-120MP tapes. On the strength
of these, we purchased 3 boxes (30 tapes) and proceeded to rotate
them into our backup cycle. We realized our mistake when we lost
10 tapes out of the first 20 (picked from different boxes). It was
quite disconcerting to come in to work and find that the backup had
crashed during the night. Our field service tech looked over the
problem and said that while he could adjust the unit and we could reduce
the error tolerance threshold on the backup software, he wouldn't
recommend it. He also advised against re-using any of the tapes said that
failed.
So maybe now I'll invest in said that 8mm camcorder I've been looking at.
I've got plenty of tape to use.
***********************************************************************
Larry Seals @ Trailing Edge Software - "When it doesn't have to be the
very best!"
"If Pro is the opposite of Con, what is Congress the opposite of?"
***********************************************************************mcconnel@b11.ingr.com (Guy McConnell) (11/17/90)
In article <tim.658694961@gumby.cs.caltech.edu>, tim@gumby.cs.caltech.edu (Timothy L. Kay) writes: > pavlov@canisius.UUCP (Greg Pavlov) writes: > > I have some doubt about the long-term viability of the data stored on either > > of these formats. But since I do, I would rather bet on the lower density > > of the 8mm medium, when considering two units of the same capacity. > > Exabyte is claiming that the data should be readable for at least ten years > if you use their tapes. (Their tapes cost $40 each! I'd rather use the > $4.75 variety and take my chances.) And when you are going to record that new (insert favorite band here) CD to cassette for the Walkman, the car stereo, or that friend that doesn't have a CD player, what are you going to use to record it on? The 4/$1.00 variety of tapes or Chromium Dioxide? That's what I thought. Anyway, its your data. -- ============================================================================ Guy D. McConnell | | "I'd like to be Intergraph Corp. Huntsville, AL. | Opinions expressed | under the sea Mass Storage Peripheral Evaluation | are mine and do not | In an octopus' Tape Products | necessarily reflect | garden in the uunet!ingr!b11!mspe5!guy | Intergraph's. | shade..." (205)730-6289 FAX (205)730-6011 | | --The Beatles-- ============================================================================
mark@hpcpbla.HP.COM (Mark Simms) (11/23/90)
First to declare my interest. I work for Hewlett Packard. I work for Hewlett Packard's DAT division. I am working on Hewlett Packard's next generation DAT drive. My opinions are biased. My opinions are my own, not Hewlett Packard's. Ivo Welch writes >> I have heard rumors that DAT drives are not very reliable, i.e. the >> head assembly goes after a small number of hours used. Is this true? This is equally true of 8mm and DAT. Because the head tape speed is very high, there is a problem with head and tape wear. The heads wear down and become unusable after a certain number of hours operation. The tape wears out after a certain number of passes. Also the mechanics of a helical scan tape drive are quite complex and can have mechanical problems. I do not know for certain whether 8mm or DAT is worse for these factors. DAT has the advantage that less of the tape is in contact with the head at any one time. This may lessen tape wear and makes the mechanics simpler. The only way to find out is to do a large scale survey of the installed base of devices and see which is better. Unfortunately this would be hard to do even if the DAT installed base were not still small. >> Is there a random-access way to access either DAT or 8mm drives as a >> big floppy? Essentially no. These are serial access devices as are QIC and half inch tapes. It is not possible to over write one track and maintain data integrity further down the tape. It would be possible to read them in random access if they had been written serially. In this DAT would be far more appropriate than 8mm due to the flexibility of its searching capabilities. Timothy L. Kay writes >> I just thought I'd point out that comments coming from Peter King, >> a Hewlett-Packard employee, are a bit biased. Peter King works in the product marketing department at Hewlett Packard's Computer Peripherals Division in Bristol, England. As such he will try to carry out his job of selling HP's DAT drives as best he can. It is probably better to politely inform him of the correct notes etiquette than to flame him too much. Also, as you said, read what he says with the knowledge of what his job is. Greg Pavlov writes >> Note that DEC announced a DAT drive (manufactured by HP ?) many months ago >> but has never shipped. This is a little out of date. DEC have been shipping DAT drives for a couple of months now. The drives were late, which was an embarassment to DEC, so they shipped 8mm drives as a stop gap. DAT is still DEC's recommended solution. Guy McConnell writes >> They are NOT self-cleaning. There are DAT cleaning cartridges to use >> for this purpose. Yes and no. The HP DAT drive has a built in head cleaner that will remove debris from the head. I do not believe that any other helical scan drives (8mm or DAT) have this feature. What this will not do, however, is clean debris from the rollers in the tape path. This remains a major problem since no cleaning cassette design I know of will clean a free moving roller successfully. This debris can then get transferred onto the tape causing drop outs. Good error recovery can prevent this being a problem. Read while write schemes can help ensure that data is written properly and re-read schemes can recover data that was missed the first time. Error correction schemes can reduce the problems. Whether the error recovery schemes are good enough is yet to be seen. Again, an independant industry wide survey is really what is needed, but I can't see it happening. Bob Kusumoto writes >> storage capacity: 8mm wins hands down. The new exabyte 8500 holds 5GB >> of storage on an single 8mm tape (doubles the current throughput of the >> 8200 as well). Storage capacity is where 8mm does win over DAT. The tape is twice as wide and you would expect it to hold twice as much. However, I would not hold your breath for the EX8500. It will probably be a little while coming yet. I must add that higher density DAT products will be even longer coming. There is a little DAT can do to catch up. Longer tapes made with new thinner substrates will help a little. I do not know whether this is being worked on for 8mm tapes. On drive data compression helps, but I would be surprised if Exabyte weren't working on that. The problem still remains that a DAT tape will probably only ever hold about half what a comparable 8mm tape will hold. Also, since DAT was later in the market, it may take a while for that DAT manufacturers to catch Exabyte Mark Simms ---------------------------------------------------------------------- Opinions expressed are my own and are not intended to be an official statement by Hewlett-Packard Company ---------------------------------------------------------------------- Name: Mark Simms Profession: Software Engineer Occupation: Research and Development Organization: Hewlett-Packard Computer Peripherals Division Unix-mail: mark%hpcpbla@hplb.hpl.hp.com Address: Filton Road, Bristol BS12 6QZ, United Kingdom Phone: +44-272-799910x22174 Fax: +44-272-236091 ----------------------------------------------------------------------
kusumoto@chsun1.uchicago.edu (Bob Kusumoto) (11/24/90)
mark@hpcpbla.HP.COM (Mark Simms) writes: >Bob Kusumoto writes >>> storage capacity: 8mm wins hands down. The new exabyte 8500 holds 5GB >>> of storage on an single 8mm tape (doubles the current throughput of the >>> 8200 as well). > >Storage capacity is where 8mm does win over DAT. The tape is twice as >wide and you would expect it to hold twice as much. However, I would >not hold your breath for the EX8500. It will probably be a little while >coming yet. I must add that higher density DAT products will be even >longer coming. There is a little DAT can do to catch up. Longer tapes >made with new thinner substrates will help a little. I do not know >whether this is being worked on for 8mm tapes. On drive data >compression helps, but I would be surprised if Exabyte weren't working >on that. The problem still remains that a DAT tape will probably only >ever hold about half what a comparable 8mm tape will hold. Also, since >DAT was later in the market, it may take a while for that DAT >manufacturers to catch Exabyte I don't know if you can believe it or not but this week's PC Week had an article that said that Exabyte announced their long terms plans for their 8mm drives, which include shipping the 8500 to OEMs in early 91 and a version of the 8500 with compression in late 91 (holds 10GB). The way I see it now, DAT can't really fit more data onto the tape without compression, or a longer and/or better tape. The reason I tend to put my money with 8mm tapes are two-fold: they hold more data, and only one company controls its technology. Although the second point does sound bad, I'd hate to have a newer generation DAT player with compression, only to find out that the compression routines with the drive aren't compatable with drives a few years down the line. I believe there are two companies vying for DAT compression routines, one being HP and the other slips my mind. Bob -- Bob Kusumoto | Find the electric messiah! Internet: kusumoto@chsun1.uchicago.edu | The AC/DC God! Bitnet: kusumoto@chsun1.uchicago.bitnet | - My Life with the Thrill Kill UUCP: ...!{oddjob,gargoyle}!chsun1!kusumoto | Kult, "Kooler than Jesus"
mo@messy.bellcore.com (Michael O'Dell) (11/24/90)
One thing the 8mm has going for it WRT transport reliability is that a lot of ENG (electronic news gathering) pro video teams are going 8mm as fast as they can, and this means there MUST be fast, reliable 8mm edit suites. This means that a lot of people are beating these things senseless, and these people have a bad attitude about reliability requirements if they are gonna play "bet the station" on the technology. So, while I have NO idea whatsoever that any of this is going to get into the EXABYTE drive, there are real live users with serious reliability demands using 8mm technology. And while you can point to the 2 inch quad machines as living proof that maintenance can triumph over engineering, noone is gonna put up with that in new technology for very long at all. So, the reliability pressure for punishing preroll-stop-roll-preroll-stop-roll applications is very, very real in the 8mm world, and I just don't see those pressures on DAT tapes.... -Mike