RE: Linux filesystem speed comparison

> -----Original Message-----
> From: Henrik Nordstrom [mailto:hno@squid-cache.org]
> Sent: Monday, April 11, 2005 6:09 PM
> To: Steven Wilton
> Cc: 'Squid Developers'
> Subject: Re: Linux filesystem speed comparison
>
> On Mon, 11 Apr 2005, Steven Wilton wrote:
>
> > We are running some large proxies in our Melbourne POP, and
> we graph the CPU
> > counters available in the 2.6 linux kernel to give us an
> idea of what the
> > CPU is doing. We noticed that the CPU was spending large
> amounts of time
> > (around 60%) in an I/O wait state, which is when the CPU is
> idle, but there
> > are pending disk i/o opeartions.
>
> Which as such isn't that harmful to Squid (aufs/diskd) as
> Squid continues
> processing requests while there is pending I/O request. But
> on the other
> hand when the disk %util level approaches 100 you reach the
> limit of what
> the drive can sustain.

My thoughts were that if the numbers for %CPU in system and user were
similar, then a "more efficient" filesystem would arrange the data on disk
in such a way that the disk spends less time performing the operations.

I will add graphs for the /proc/diskstats value that records the amount of
time the disk is actually performing operations, and see how this compares
across the different filesystems (I looked at the iostat source to see how
it calculates the %util value).

Regards

Steven

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