FreeBSD 5.3 I/O Performance / Linux 2.6.10 | Continued Discussion

Robert Watson rwatson at
Fri Jan 28 01:53:12 PST 2005

On Thu, 27 Jan 2005, Mike Tancsa wrote:

> >I/O (reads, writes at fairly large multiples of the sector size -- 512k is
> >a good number) and small I/O size (512 bytes is good).  This will help
> >identify the source along two dimmensions: are we looking at a basic
> >storage I/O problem that's present even without the file system, or can we
> >conclude that some of the additional extra cost is in the file system code
> >or the hand off to it.  Also, with the large and small I/O size, we can
> >perhaps draw some conclusions about to what extent the source is a
> >per-transaction overhead.
> Apart from postmark and iozone (directly to disk and over nfs), are
> there any particular tests you would like to see done ? 

Just to get started, using dd to read and write at various block sizes is
probably a decent start.  Take a few samples, make sure there's a decent
sample size, etc, and don't count the first couple of runs.

Robert N M Watson

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