On Tue, Mar 21, 2000 at 09:29:56AM -0800, Matthew Dillon wrote:
> :>
> :> I would think that track-caches and intelligent drives would gain
> :> much if not more of what clustering was designed to do gain.
> :
> :Hm. But I'd think that even with modern drives a smaller number of bigger
> :I/Os is preferable over lots of very small I/Os. Or have I missed the point?
> As long as you do not blow away the drive's cache with your big I/O's,
> and as long as you actually use all the returned data, it's definitely
> more efficient to issue larger I/O's.
Prefetching data that is never used is obviously a waste. 256K might be a
bit big, I was thinking of something like 64-128Kb
Drive caches tend to be 0.5-1Mbyte (on SCSI disks) for modern drives.
I happen to hate write-caching on disk drives so I did not consider that as
a factor.
> If you generate requests that are too large - say over 1/4 the size of
> the drive's cache, the drive will not be able to optimize parallel
> requests as well.
True.
--
Wilko Bulte Arnhem, The Netherlands
http://www.tcja.nl The FreeBSD Project: http://www.freebsd.org
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