tms@cup.portal.com (Alexis TMS Tatarsky) (04/09/90)
Sometime back I requested information regarding high capacity backup media. Thanks to all who responded. The majority of the respondents pointed me in the way of Exabyte 8mm technology. Some pointed me towards the R-DAT technology. Those who were using the 8mm technology were, for the most part, happy whith their purchase. The R-DAT proponents mentioned that this technology would surpass the 8mm technology in the near future. I believe this to be true. For one, only one manufacturer (Exabyte) has gotten into the 8mm game. Also, many computer manufacturers (HP for instance) are going with R-DAT as standard product. My question is why??? 8mm has a higher capacity, is faster, and as far as I know reliable (even though early Exabyte units proved extremely unreliable). ok Any insight as to why R-DAT is technologically the way to go would be extremely appreciated. Ric Urrutia Taos Mountain Software tms@cup.portal.com
kaufman@Neon.Stanford.EDU (Marc T. Kaufman) (04/09/90)
In article <28719@cup.portal.com> tms@cup.portal.com (Alexis TMS Tatarsky) writes: >...Also, many computer >manufacturers (HP for instance) are going with R-DAT as standard product. >My question is why??? 8mm has a higher capacity, is faster, and as far as I >know reliable (even though early Exabyte units proved extremely unreliable). Part of the problem is that Exabytes are faster. Many SCSI systems just cannot keep the Exabyte streaming at 240+ KB/sec AND read the disk at the same time. The slower DAT system (125 KB/sec I think) gives the OS more time to read and format disk data without dropping out of streaming mode. Marc Kaufman (kaufman@Neon.stanford.edu)
buck@siswat.UUCP (A. Lester Buck) (04/09/90)
In article <28719@cup.portal.com>, tms@cup.portal.com (Alexis TMS Tatarsky) writes:
< My question is why??? 8mm has a higher capacity, is faster, and as far as I
< know reliable (even though early Exabyte units proved extremely unreliable).
< Any insight as to why R-DAT is technologically the way to go would be
< appreciated.
I don't think it has anything to do with technology, per se. It is simply a
size issue. R-DAT will fit in a 3.5" form factor, so the market for these
drives will be an order of magnitude larger.
--
A. Lester Buck buck@siswat.lonestar.org ...!texbell!moray!siswat!buckgil@jtsv16.UUCP (gil) (04/09/90)
In article <1990Apr9.013326.11270@Neon.Stanford.EDU>, kaufman@Neon.Stanford.EDU (Marc T. Kaufman) writes: > In article <28719@cup.portal.com> tms@cup.portal.com (Alexis TMS Tatarsky) writes: > .. The slower DAT system (125 KB/sec I think) gives the OS more ^^^ > time to read and format disk data without dropping out of streaming mode. Typically, transfer rates to a DAT are closer to 192KB/sec. This is a little closer to the 240KB/sec for 8mm units. +-----------------------------+-------------------------------------------+ | Gil Hauer | | | Tech Noir Inc. | gil@jtsv16.jts.com | | Toronto +1 416 653-8276 | or: uunet!jtsv16!gil | +-----------------------------+-------------------------------------------+
mcconnel@b11.ingr.com (Guy McConnell) (04/10/90)
In article <28719@cup.portal.com>, tms@cup.portal.com (Alexis TMS Tatarsky) writes: > Sometime back I requested information regarding high capacity backup > media. Thanks to all who responded. > > The majority of the respondents pointed me in the way of Exabyte 8mm > technology. Some pointed me towards the R-DAT technology. Those who > were using the 8mm technology were, for the most part, happy whith their > purchase. > > The R-DAT proponents mentioned that this technology would surpass the 8mm > technology in the near future. I believe this to be true. For one, only > one manufacturer (Exabyte) has gotten into the 8mm game. Also, many computer > manufacturers (HP for instance) are going with R-DAT as standard product. The key to this lies in the words "R-DAT proponents". Now, you wouldn't expect these people to tell you that a competing technology was better than their own, would you? Technically there is only one manufacturer of 8mm drives, however, Kubota of Japan manufactures ~60% of all 8mm drives made under license to Exabyte. They also have the licensed ability to sell to the Pacific rim. One of the reasons that there aren't more players in the 8mm market is that Exabyte owns patents on most of the technology that makes the drive suitable for data storage. R-DAT is a CONSUMER based product that still uses much of the audio recording hardware and encoding schemes in the data storage device. One of the penalties of this is the comparitively high probability of significant capacity loss on the 4mm device if error correction has to be invoked (as it inevitably will: this is, after all, tape we are talking about). For the record, Exabyte has licensed the DDS format (the HP/Sony format) and could, due to the ready availability of the hardware, bring a 4mm product to market in a very short time should it prove to be warranted. The 4mm vendors would have to spend a large amount of time and money to develop an 8mm device because it would have to be designed from the ground up and, with Exabyte's huge lead in the marketplace, the catch up game is probably out of reach for them. As for the reason that HP is "going with R-DAT as a standard product", they jointly developed both the drive and DDS format with Sony so one would expect them to use it. > My question is why??? 8mm has a higher capacity, is faster, and as far as I > know reliable (even though early Exabyte units proved extremely unreliable). > ok > Any insight as to why R-DAT is technologically the way to go would be extremely > appreciated. 8mm does indeed have a capacity and speed advantage over R-DAT drives and that lead has recently been extended with the announcement of a 5Gb drive which will be read AND write compatible with the current product and will transfer data at 500Kb/sec. As to the liklihood that R-DAT will surpass 8mm technology, it would have to be a very stretched definition of "surpass" to fit. The 4mm format is currently at saturation and the data is actually written so that data from adjacent tracks overlaps. The azimuth of the adjacent tracks is different so that the drive can line up on the correct track. The only way that they can increase capacity is via compression, longer (and therefore thinner) tapes, or a combination of the two. These two alternatives can also be applied to the 8mm format as well but, because the 8mm tape format is only at about 70% saturation with the 5Gb model, I would expect to see further capacity increases on it without using either. It would seem unlikely that R-DAT will surpass 8mm in capacity. Right now, R-DAT is the "new and sexy" technology and it will be interesting to see how well it stands up in the real world of data storage as the number of drives shipped increases. I personally think that the two will coexist in the storage marketplace with the R-DAT product filling a niche below the 8mm device. Guy McConnell | The above is my opinion and may not Intergraph Corp. | reflect the opinion of Intergraph. Mass Storage Peripheral Evaluation | Tape Specialist |
seymour@milton.acs.washington.edu (Richard Seymour) (04/10/90)
the MAJOR difference is that DAT tapes are block-addressable (like old DECtapes).. so you can random-access anywhere on the 1.2 Gbytes within about 40 seconds. In our application that's very attractive -- but not currently supported by normal DEC utilities (except on PDP-8's, PDP 11/20's, etc. :-) but an 8mm drive system which will use fast-seek can get to the 1.2 Gbyte marker in only 6 minutes. which is blindly fast compared to the load/shuffle time of a 6250bpi 9-track drive -- even if you mount the correct reel first! --dick
mcconnel@b11.ingr.com (Guy McConnell) (04/10/90)
In article <526@siswat.UUCP>, buck@siswat.UUCP (A. Lester Buck) writes: > In article <28719@cup.portal.com>, tms@cup.portal.com (Alexis TMS Tatarsky) writes: > < Any insight as to why R-DAT is technologically the way to go would be > < appreciated. > > I don't think it has anything to do with technology, per se. It is simply a > size issue. R-DAT will fit in a 3.5" form factor, so the market for these > drives will be an order of magnitude larger. The 8mm drive will also fit into a 3.5" form factor. Keep your eyes and ears open. So much for the order of magnitude... Guy McConnell Intergraph Corp. Huntsville, AL.
terryk@pinocchio (Terence Kelleher) (04/10/90)
I just get the feeling that some basic points are being lost when the 8mm vs. 4mm issue comes up. Here my 2 cents, all 1 cent worth of it. Sometime, take a good look at the tape path taken in an 8mm drive. 270 degrees of wrap around the head, and you can see where the tape buckles and contorts to fit around. The mechanism stresses the tape. The head and the basic electronics were all designed with video in mind, where track-to-track isolation is of little concern. Exabyte did some good work in getting this to run for Data, but its still a video deck. They did not change the basic mechanicals. The 4mm drives started from the ground up with digital data in mind. Although they are lower capacity now, they have room for expansion as the technology improves. The tape path is short. The tape does not get flexed and bent and stretched. You get the feeling from looking at the insides like maybe this thing can run a tape 3 or 4 hundred times without breaking it. -- Terence Kelleher Encore Computer Corporation terryk@encore.com