mcia@uhura.cc.rochester.edu (Mike Ciaraldi) (09/30/90)
I'm helping someone configure a multi-user Unix system. We're looking at a 486 running at 33 MHz, with 16 Megabytes RAM and 16 serial ports. It will be used to run accounting software. We want to put on about 400 Megabytes of disk, but I'm trying to decide what is the best interface. My first thought was to use an intelligent disk controller (such as the one made by DPT), containing 256 kilobytes of cache, connected to the disk drive by ESDI. I figured the disk caching would speed up access to the programs and data files, by keeping sectors recently read from the disk and even pre-fetching sectors. On the other hand, I keep hearing that SCSI is a superior interface. But does the faster data-transfer rate compensate for the lack of caching? Or are there SCSI drives that include caching? Does anyone have any comments on making this choice, or experience in this sort of setup? There does not seem to be much of a cost difference, so I am looking for the choice that will give the best performance. You can post back to this newsgroup, or reply to me at: ciaraldi@uhura.cc.rochester.edu
feustel@netcom.UUCP (David Feustel) (09/30/90)
Get an IDE controller and hang two (conner) 200 meg drives on it. Each drive has its own 64k buffer and the transfer rate between drive and cpu is up to 4mbyte/sec. You then will have no problems running any software that expects an MFM controller since they have the same interface. -- David Feustel, 1930 Curdes Ave, Fort Wayne, IN 46805, (219) 482-9631
davidsen@sixhub.UUCP (Wm E. Davidsen Jr) (10/01/90)
In article <9678@ur-cc.UUCP> mcia@uhura.cc.rochester.edu (Mike Ciaraldi) writes: | Does anyone have any comments on making this choice, or experience | in this sort of setup? There does not seem to be much of a cost | difference, so I am looking for the choice that will give the | best performance. In my experience and from talking to 10-15 people running UNIX on a PC of some kind, and from "big UNIX" I would say access time is far more important than transfer rate unless you are processing large data sets. I mean accessing them, not just getting a few records from a big database. Therefore you can go RLL, ESDI or SCSI and most of the performance changes will come from access time. If you go ESDI we have found at work that the CompuAdd cached controller is quite good. Not because of the cache, UNIX does cache quite well and shows only about 2:1 speedup even with 4MB, but because it seems to handle any ESDI disk we have tried. Obviously you want a minimum of track buffering... -- bill davidsen - davidsen@sixhub.uucp (uunet!crdgw1!sixhub!davidsen) sysop *IX BBS and Public Access UNIX moderator of comp.binaries.ibm.pc and 80386 mailing list "Stupidity, like virtue, is its own reward" -me
alexis@panix.uucp (Alexis Rosen) (10/02/90)
In article <14174@netcom.UUCP> feustel@netcom.UUCP (David Feustel) writes: >Get an IDE controller and hang two (conner) 200 meg drives on it. >Each drive has its own 64k buffer and the transfer rate between drive >and cpu is up to 4mbyte/sec. You then will have no problems running >any software that expects an MFM controller since they have the same >interface. This is really bogus. The connors drives are 3.5" mechanisms. So their transfer rate is really lousy compared to 5.25" disks. Seek's pretty good, but not best. (Transfer's respectable for a 3.5"- it's not poorly-built.) I can't tell you much about PC host adaptors, but if you want really fast: 1) Make sure you get two disks (or more) so you can share the load. Make sure that, at the very least, swap is on a different drive than your most commonly-used data files. 2) SCSI is unquestionably the interface of the future. For now? Well, it looks pretty damn good. The best drive I know of in your range is the 400MB drive from Imprimis (Seagate). But, you might well do better with two 170MB drives. (These are all Wrens.) It really depends on your situation. If you really want speed at a decent price, get two Wren Runners for a total of 600MB. They can be had for about $1800 apiece or less. The 400 is about $2600- more expensive, and a little slower than the Runners, since the 400 is a half-height mechanism. 3) The Wren Runner has the fastest true average seek time of any mechanism I know. They claim 10.7ms, I say 11-12 depending on the unit. Of course, if you really have a need for speed, the new Imprimis Elites, starting at 1.5GB, are incredible. Still hard to come by though. Almost forgot- most of these Wrens have small caches. In general, you'd do better by putting more memory in your unix box than by buffering the disk. In particular, you can throw on a good 16MB in SIMMs for ~$1000 these days, plus the price of a memory board. Much cheaper than the cache cards I've seen. Don't forget that you could always use this memory as a buffer cache. Also, you'll need to make sure that your unix will talk to your controller card. --- Alexis Rosen {cmcl2,apple}!panix!alexis alexis@panix.uucp
feustel@netcom.UUCP (David Feustel) (10/10/90)
Specs from the Conner IDE Disk Drive Manual: Drive: CP3204 (200 mb) Ave Seek Time: 19 ms. Data Transfer Rate: (To/From Media) 1.5 Mbyte/second (Across Interface) 4.5 MByte/second -- David Feustel, 1930 Curdes Ave, Fort Wayne, IN 46805, (219) 482-9631