Hi,
On Mon, 26 Apr 1999 21:28:20 +0100 (IST), Paul Jakma <[EMAIL PROTECTED]>
said:
> it was close between 32k and 64k. 128k was noticably slower (for
> bonnie) so i didn't bother with 256k.
Fine, but 128k will be noticeably faster for some other tasks. Like I
said, it depends on whether you prioritise large-file bandwidth over the
ability to serve many IOs at once.
> viz pipelining: would i be right in thinking that a decent scsi
> controller and drives can "pipeline" /far/ better than, eg, a udma
> setup?
Yes, although you eventually run into a different bottleneck: the
filesystem has to serialise every so often while reading its indirection
metadata blocks. Using a 4k fs blocksize helps there (again, for
squeezing the last few %age points out of sequential readahead).
> ie the optimal chunk size would be higher for a scsi system than for
> an eide/udma setup?
udma can do readahead and multi-sector IOs. scsi can have limited
tagged queue depths. Command setup is more expensive on scsi than on
ide. Which costs dominate really depends on the workload.
--Stephen
