Date: Wed, 17 Sep 1997 09:38:38 +1200 From: physmsa AT cantua DOT canterbury DOT ac DOT nz (Mr M S Aitchison) Subject: SCSI disks, NWCACHE and fragmented disks (was Re: ClosedDOS??? To: opendos AT delorie DOT com Message-id: <199709162138.JAA17917@cantua.canterbury.ac.nz> Precedence: bulk -= ArkanoiD =- wrote: > > btw NWCACHE slows down terribly on fragmented disks. I'd like to find out more details, e.g. how much RAM was being used by the cache, how big the disk is, how many buffers are defined in config.sys, etc. It is often said that you can take the buffers down to something really low, e.g. 2, when you have a cache. This isn't exactly true. It still helps to keep the buffers at something like the number of files in the largest directory in your path divided by 16. This seems to be especially true if the amount of RAM the cache gets is below a couple of Mb and/or you are wasting the cache by reading large amounts of data that rarely is needed again. I find that usually NWCACHE does a very good job, better than most, but all caching algorithms make assumptions about how likely certain blocks are to be needed again soon. Having buffers set high (use up all of the remaining HMA at least) ensures that one important area - the directory - is pretty likely to stay in RAM. If NWCACHE isn't working well for you I'd love to know why not, so please let me know if increasing the buffers to over 20 (preferrably 40) helps, and any other details of your setup you can feed into an email message! Christopher Croughton wrote: > I haven't bothered with SCSI. Why pay twice as much for no noticable > improvement over EIDE? SCSI disks are much better in some situations, for example Linux can arrange several disk requests at the same time. Normally, DOS-like operating systems cannot do this (I'm thinking hard how OpenDOS could be made to; feel free to jump in with suggestions). Even so, there are still some throughput advantages with SCSI in that EIDE's quoted maximum throughput is often a long way from what you actually get, whereas a good SCSI controller and disk can be expected to come close to the maximum. Be careful not to go by published specs, but real life situations... I'd agree that, with (Open)DOS at the moment and typical legacy applications, you *probably* will find the extra cost of SCSI is better spent in RAM or CPU speed, but most Linux owners (whether or not they are servers, know SCSI is a good investment. ------------------------------------------------------------------------------- Mark Aitchison, Physics & Astronomy \_ Phone : +64 3 3642-947 a.h. 3371-225 University of Canterbury, (/' Callsign: ZL3TQE -------------------------------------------------------------------------------