RE: Linux filesystem speed comparison

From: Henrik Nordstrom <>
Date: Tue, 12 Apr 2005 09:04:41 +0200 (CEST)

On Tue, 12 Apr 2005, Steven Wilton wrote:

> 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.

Partly true, but the problem is that the %IOWAIT is quite voilatile and
hard to make any reliable readings due to %USER and %SYS stealing time
from %IOWAIT, making things very timing dependent, and even more so as the
load increases.

%IOWAIT works great for single-threaded blocking disk I/O applications
(i.e. if using the ufs or coss cache_dir driver), but not so good in
applications where I/O is done in some non-blocking fashion (i.e. aufs or
diskd cache drivers).

> 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).

Looking forward to see your results.

Received on Tue Apr 12 2005 - 01:04:43 MDT

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