Xref: utzoo comp.periphs.scsi:2983 comp.unix.questions:32445 Newsgroups: comp.periphs.scsi,comp.unix.questions Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!sdd.hp.com!news.cs.indiana.edu!maytag!watmath!watdragon!rose.waterloo.edu!sasingh From: sasingh@rose.waterloo.edu (I-I-Ice -now that's refreshing.) Subject: how to maximize performance? Message-ID: <1991Jun26.181856.5343@watdragon.waterloo.edu> Keywords: SCSI, adaptec, ST296N, CDC Wren. Sender: news@watdragon.waterloo.edu (News Owner) Organization: University of Waterloo Date: Wed, 26 Jun 1991 18:18:56 GMT Lines: 63 Could someone help me please? I have been trying to figure out the best way to install 386ix and I am confused. My system has an Adaptec 1542B, 4 megs of ram, with device 0 being the ST296N (access time 28 ms) and device 1 the CDC (access time 18 ms). I would like to put the Unix system itself on half of one of the drives (I currently have 2 40 meg partitions on the 296N, and I would like to do the same for the CDC), and put my user files on the other drive. If I understand this correctly, then SCSI can send multi-threaded I/O requests which can be processed by both devices simultaneously, rather than all the I/O burden on one drive. As the cliche goes, two heads are better than one. But all this would be easy if the drives were the same, but they are not; there are performance differences; and I do not know what portion of Unix to put on which drive to guarantee best performance. Transfer rates for the two drives are: 296N: I/O Trans. Rate (Mbytes/sec) 1.5 Int. Trans. Rate (Mbits/sec) 10 CDC: I/O Trans. Rate (Mbytes/sec) 1.25 Int. Trans. Rate (Mbits/sec) 10 Finally, here is a transcript of a conversation with a friend of mine about this. Please reply to me privately, and if justified, I will re-post. Thanks very much. Ice. ----------------------------------------- sasingh> Also question. Would it not make more sense to install Unix on sasingh> the CDC Wren, since it has the faster mechanical access time? sasingh> Unix is about 200 little programs, so a high transfer rate is sasingh> not as important as finding the data quickly. That would be true, but ... sasingh> And swap space would be better utililized by the 296N since it sasingh> has a slightly higher transfer rate than the CDC, but a slower sasingh> access time; but since swap space is one big chunk, the slower sasingh> seek time should not be a liability, since the head is usually sasingh> going to be centered right at the beginning of the swap file sasingh> right? Well, actually, it depends on how they implement swap. But, I'm pretty sure that typically, the disk has to see back and forth to get to the appropriate swap sector, and then read it. You swap is big, right? But any swap block is relatively small. As for Unix being lot's of small files, that is true. But one small file load will not matter much if you start swapping. You'll notice a significant speed decrease when you start swapping (as you could probably guess) so optimizing that is more important. As least that's how I'd do it.