dougie@its63b.ed.ac.uk (Dougie Nisbet) (02/03/88)
We are intending buying a PC clone with 40 Megabytes of disk space. Is it more sensible to buy 2 X 20 Meg, or 1 X 40 Meg drives? I have heard rumours that the 2X20's run faster than 1X40. Does anyone know if this is in fact the case? Any other reasons for/against would also be appreciated. -- Dougie Nisbet Medical Statistics Unit | UUCP: ...seismo!mcvax!ukc!ed!dougie University of Edinburgh | JANET: dougie@uk.ac.ed.emas-a Teviot Place Edinburgh United Kingdom
bcw@rti.UUCP (Bruce Wright) (02/05/88)
In article <950@its63b.ed.ac.uk>, dougie@its63b.ed.ac.uk (Dougie Nisbet) writes: > We are intending buying a PC clone with 40 Megabytes of disk space. > Is it more sensible to buy 2 X 20 Meg, or 1 X 40 Meg drives? I have > heard rumours that the 2X20's run faster than 1X40. Does anyone know if > this is in fact the case? Any other reasons for/against would also be > appreciated. > As with many things, there are several sides to this. The major advantages of one drive are: 1) The large drives tend to have lower average access times than the small drives (that is, the mechanism itself is higher quality) 2) A large drive tends to be less subject to disk fragmentation than two small drives (therefore files are more contiguous => less head motion to read files) 3) The larger drives (as a group) are higher quality drives with a larger MTBF. The major advantages of two drives are: 1) If one drive goes down you can always use the other drive 2) It is probably cheaper to replace one small drive which goes bad than to replace one large drive which goes bad On the PC it will be rare that two small drives will be faster than one large drive (exception: if the large drive's average access time is about equal to the average access time of the small drive AND the operating system/ disk controller you are running supports overlapped seeks THEN MAYBE the two small drives can outrun the large one ... note that this excludes all the major PC system software (MS-DOS, Concurrent DOS, most UNIX systems, etc) and many disk controllers). Also, if you are using DOS 2.*, the file allocation routines are sufficiently stupid that the one large drive would suffer disproportionately (assuming that you allocated with sector sizes > 512 bytes so that you could use the whole drive). For the vast majority of cases the one large drive will be faster. When we put 40 MB on an old XT we put two small drives in because we were concerned with system availability at the expense of convenience and speed. (yes, yes, I know, p(one drive out of two going bad) > p(one drive out of one going bad) but p(two drives out of two going bad) < p(one drive out of one going bad) even if the MTBF of the two drives is much lower than the MTBF of the large drive -- remember I'm talking about whether the system is useable even in a degraded mode and for our purposes a floppy-only system even for a couple of weeks would not be a useable mode). Anyway, I'm not sure we would make the same choice now - the Seagate 225 drives we used have been a lot of trouble. If we were doing the system over again we might go for a real high-reliability single drive (Core, Maxtor, or something similar), with the possibility of buying a cheap small drive for when the big drive died. This can of course be considerably more expensive than even the two-drive solution - but I would definitely recommend _against_ going with a single large drive and making it a cheap drive - you are really asking to take a big hit when (not if) the drive goes bad. Bruce C. Wright
berger@clio.las.uiuc.edu (02/06/88)
On an AT class machine, the only speed advantage you'd get from two
separate drives is if you could make one seek while accessing the
other. The standard disk controllers don't allow this.
A single drive has the advantage of occupying less space,
generating less heat, and consuming less power.
If speed is a big consideration, get a drive with a fast
step rate and seek time.
Mike Berger
Department of Statistics
Science, Technology, and Society
University of Illinois
berger@clio.las.uiuc.edu
{ihnp4 | convex | pur-ee}!uiucuxc!clio!bergerskl@van-bc.UUCP (Samuel Lam) (02/07/88)
In article <16800198@clio>, berger@clio.las.uiuc.edu wrote: >A single drive has the advantage of occupying less space, >generating less heat, and consuming less power. But having two 20 Meg drives instead of a single 40 Meg drive has the advantage that if one of them ever fails and has to be sent to the shop for repair, you can still run your system with 20 Meg, instead of *zero* Meg! (This, of course, assumes that you have done proper backups on the drive that went south.) ...Sam -- Samuel Lam <Samuel.Lam@van-bc.UUCP> or {ihnp4!alberta,watmath,uw-beaver}!ubc-vision!van-bc!skl
madd@bu-cs.BU.EDU (Jim Frost) (02/08/88)
In article <950@its63b.ed.ac.uk> dougie@its63b.ed.ac.uk (Dougie Nisbet) writes: >We are intending buying a PC clone with 40 Megabytes of disk space. >Is it more sensible to buy 2 X 20 Meg, or 1 X 40 Meg drives? I have >heard rumours that the 2X20's run faster than 1X40. Does anyone know if >this is in fact the case? Any other reasons for/against would also be >appreciated. This is a hard question to answer, but here are some things that may help you choose. Speed. 2 20Mb drives can operate faster than 1 40Mb drive merely because you can be splitting data between more platters/heads. This becomes a consideration if you use software to configure both drives as a single logical drive. Several software packages do this, although I have only used Bow Systems VFeature. Note that most 20Mb drives are slower than 40Mb drives, so you may actually lose performance if you use 20Mb disks and you'll probably loose performance if you use each 20Mb disk as an independent logical drive since it will be impossible to split data between the two drives for faster access. Configuration. Both 40Mb and 2x20Mb systems would have to be divided into 2 logical drives if you don't use a software package to overcome the MS-DOS 32Mb logical drive size limitation. This can have profound affects on your software. A single 40Mb disk is much more flexible, though. You could make one 32Mb logical drive for data and place all programs on the 8Mb partition. This would speed backups since you need only back up the program partition when you add a new program. Reliability. One of two drives is more likely to fail than a single drive. Unless you're using software to make a large logical drive on two separate physical drives, having two small drives means your system will still have a drive while you repair/replace the failed drive, while having only one will leave you out of luck. It is important to note that higher storage drives tend to be newer and use more reliable technology, which means that it's less likely that one 40Mb drive is going to fail than one 20Mb drive. This is not universally true but it's a good rule of thumb. Taking each of these factors into consideration, it would seem that a larger disk would be slightly more reliable than several smaller ones. If you cannot risk down time, having more than one drive might be a deciding factor since your system will still be running even if one drive fails, although in a crippled state. Conclusion. I would recommend a single 40Mb drive. This tends to be less expensive than 2 20Mb drives (although not much) and would leave the controller open for an additional drive later should you need it. It also will be less demanding on your power supply. Each other factor depends on the type of drive you order and your particular needs, but in general larger drives are faster and more reliable than smaller ones due to improvements in technology over time. jim frost madd@bu-it.bu.edu
mpatnode@polyslo.UUCP (Mike Patnode) (02/09/88)
In article <19754@bu-cs.BU.EDU> madd@bu-it.bu.edu (Jim Frost) writes: >In article <950@its63b.ed.ac.uk> dougie@its63b.ed.ac.uk (Dougie Nisbet) writes: >>We are intending buying a PC clone with 40 Megabytes of disk space. >>Is it more sensible to buy 2 X 20 Meg, or 1 X 40 Meg drives? I have >>heard rumours that the 2X20's run faster than 1X40. Does anyone know if >>this is in fact the case? Any other reasons for/against would also be >>appreciated. > >This is a hard question to answer, but here are some things that may >help you choose. .. many pros and cons concerning drives deleted... Actually this is very easy to answer: The seagate 4051 is a 40Meg Harddisk wich runs at 39ms.(access time) If you partition the disk into two 20 Meg disks it then runs at 28ms. There is the speed you want on the security of one disk. If your like me and you don't want to have to switch between C: and D: all the time try: JOIN D: \USR and then you have a disk mounted as a file system. For the software that doesn't like joined disks IE:NU and QDOS use: JOIN D: /D before calling these programs. Hope this helps. -- Mike "Dodger" Patnode | (n) ..csustan!polyslo!mpatnode Yitbos Innovations Inc. | (s) ..sdsu!polyslo!mpatnode 244 California Blvd | mpatnode@polyslo.UUCP San Luis Obispo, Ca 92630 | (805) 541-2048 / 543-9818 / 756-2516
mhc@arrow.UUCP (MH Cox) (02/10/88)
In article <1666@van-bc.UUCP> skl@van-bc.UUCP (Samuel Lam) writes: >In article <16800198@clio>, berger@clio.las.uiuc.edu wrote: >>A single drive has the advantage of occupying less space, >>generating less heat, and consuming less power. > >But having two 20 Meg drives instead of a single 40 Meg drive has >the advantage that if one of them ever fails and has to be sent to >the shop for repair, you can still run your system with 20 Meg, >instead of *zero* Meg! (This, of course, assumes that you have >done proper backups on the drive that went south.) > >...Sam Also, I've discovered that is you put all compilers, linkers, etc. on one disk and your source files on the other, your compile times will decrease (compared to one disk). I assume this is caused by reducing the number of seeks that must be performed. -- Michael H. Cox (201) 580-8622
brianc@cognos.uucp (Brian Campbell) (02/12/88)
In article <950@its63b.ed.ac.uk> dougie@its63b.ed.ac.uk (Dougie Nisbet) writes: > We are intending buying a PC clone with 40 Megabytes of disk space. > Is it more sensible to buy 2 X 20 Meg, or 1 X 40 Meg drives? I have > heard rumours that the 2X20's run faster than 1X40. Does anyone know if > this is in fact the case? Any other reasons for/against would also be > appreciated. Having two drives does have its advantages. Any programs (or data) that doesn't change, shrink or grow, can remain on one drive, while everything else remains on the other. This affects program startup time mostly, but can also improve performance on programs which access files on the drive which doesn't get fragmented. If you're in a multi-tasking or multi-user environment, having two independent controllers may also be an asset (perhaps even if you're not?). -- Brian Campbell uucp: decvax!utzoo!dciem!nrcaer!cognos!brianc Cognos Incorporated mail: POB 9707, 3755 Riverside Drive, Ottawa, K1G 3Z4 (613) 738-1440 fido: (613) 731-2945 300/1200, sysop@1:163/8
ugfailau@sunybcs.uucp (Fai Lau) (02/18/88)
In article <2276@cognos.UUCP> brianc@cognos.UUCP (Brian Campbell) writes: > >Having two drives does have its advantages. Any programs (or data) >that doesn't change, shrink or grow, can remain on one drive, while >everything else remains on the other. This affects program startup >time mostly, but can also improve performance on programs which access >files on the drive which doesn't get fragmented. > But if you partition the disk into 2 200meg virtual disk you accomplish the same thing. HOWEVER, I don't know of any unfragmentation program that works on _part_ of a disk, be it a virtual drive or selected tracks. Does anyone know? My hard disk has about 60% stationary data and mace does the same sh*t everytime.... Fai Lau SUNY at Buffalo (The Arctic Wonderland) UU: ..{rutgers,ames}!sunybcs!ugfailau BI: ugfailau@sunybcs INT: ugfailau@joey.cs.buffalo.EDU
dick@slvblc.UUCP (Dick Flanagan) (02/19/88)
In article <8641@sunybcs.UUCP> ugfailau@sunybcs.uucp (Fai Lau) writes: > My hard disk has about 60% stationary data and mace does the same > sh*t everytime.... Mark your "stationary data" read-only and Mace will try to collect it all toward the physical beginning of the disk. The theory behind this is that subsequent defrag' operations will go over this area relatively quickly since it should not have become fragmented. Dick -- Dick Flanagan, W6OLD GEnie: FLANAGAN UUCP: ...!ucbvax!ucscc!slvblc!dick Voice: +1 408 336 3481 Internet: slvblc!dick@ucscc.UCSC.EDU LORAN: N037 04.7 W122 04.6 USPO: PO Box 155, Ben Lomond, CA 95005
kleonard@PRC.Unisys.COM (Ken Leonard --> kleonard@gvlv2@prc.unisys.com) (02/20/88)
In article <8641@sunybcs.UUCP> ugfailau@joey.UUCP (Fai Lau) writes: > But if you partition the disk into 2 20meg virtual disk >you accomplish the same thing. HOWEVER, I don't know of any >unfragmentation program that works on _part_ of a disk, be >it a virtual drive or selected tracks. There are at least two programs which WILL defrag a "virtual disk", assuming that what we really mean is an operating-system partition (as in FDISK) or (as a FEW controllers do) a controller-defined virtual-addressed below-low- level partition. They are: VOPT -- by Golden Bow -- see back pages of "PC" and/or "BYTE" and/or etc. DOG (Disk OrGanizer) -- by G. Allan (Allen?) Morris -- see you local BBS. I have successfully used both of them in both of the situations I have described. VOPT does a FAST, best-fit cram of whatever and wherever and however is on the disk. DOG does a not-extermely fast, nice-default fit or YOUR-OWN-specified fit, cram of whatever you want to wherever you want in the order you want. Regardz, Ken Leonard --- This represents neither my employer's opinion nor my own: It's just something I overheard in a low-class bar down by the docks.
toma@tekgvs.TEK.COM (Tom Almy) (02/23/88)
In article <8641@sunybcs.UUCP> ugfailau@joey.UUCP (Fai Lau) writes: > But if you partition the disk into 2 200meg virtual disk >you accomplish the same thing. HOWEVER, I don't know of any >unfragmentation program that works on _part_ of a disk, be >it a virtual drive or selected tracks. Golden Bow's VOpt program only moves files if it will improve performance, thus if the disk has no fragments and no holes big enough to hold any files currently more distant then it does nothing! It is fast enough that you can put it in your AUTOEXEC.BAT. It may not do a *perfect* job of rearranging, but it does 99% of what those slow utilities end up with. Tom Almy toma@tekgvs.TEK.COM
davejag@wybbs.UUCP (Dave Jaglowski) (02/26/88)
In article <3145@tekgvs.TEK.COM>, toma@tekgvs.TEK.COM (Tom Almy) writes: > In article <8641@sunybcs.UUCP> ugfailau@joey.UUCP (Fai Lau) writes: > > But if you partition the disk into 2 200meg virtual disk > >you accomplish the same thing. HOWEVER, I don't know of any > >unfragmentation program that works on _part_ of a disk, be > >it a virtual drive or selected tracks. > > Golden Bow's VOpt program only moves files if it will improve performance, > Tom Almy > toma@tekgvs.TEK.COM I am using PCTOOLS compress with my HD (20Meg) Partitioned into 2 10 Meg Drives.All the utilities that I have used, mainly COMPRESS, work on any virtual (Let's use the standard terms here: Logical drive, as opposed to physical drive) drive. They just use the sector maps they have for that drive so (using mine as an example:) Tracks 0-306: Partition 1 Tracks 307-613: Partition 2 If you compress partition 2, you will not affect the data on partition 1. I'm not sure if any utilities CAN bypass this partitioning. ______________________________________________________________________ WYBBS: SCO XENIX Grand Rapids, Michigan Phone: (616) 457-1964 UUCP: Ihnp4!killer!Wybbs!Davejag --- Dave Jaglowski - (616)676-2647 "Fer cryin' out loud... Research physcisits need Porches too!" - Opus ----------------------------------------------------------------------