Re: poor performance on big machine

["Steve O'Hara-Smith" <steve@xxxxxxxxxx>]

On Mon, 30 Jul 2007 09:57:11 -0700 (PDT)
Matthew Dillon <dillon@apollo.backplane.com> wrote:

>     I don't think an I/O scheduler will help.  You are maxing out the hard
>     drive with your workload.  MB/sec is irrelevant... the workload is 
>     causing the disk to seek a lot.

	If it is thrashing between a small number of areas then it may be
possible to improve things with a scheduler that buffers and attempts to
cluster the requests by track (OK address proximity). In extreme cases
going from one operation per seek to two operations per seek would be a
big gain.

	Of course this is likely to interfere with any "has been committed
to disc" semantics needed.

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