[CentOS] Wrties starving reads (was: re:Shrinking a volume group)

[Steve Bergman]

On Wed, 2006-09-13 at 13:15 -0500, Steve Bergman wrote:

> Interestingly enough, I cannot reproduce the writes starving reads
> problem on my desktop Ubuntu Dapper box running "2.6.15-26-k7 #1 SMP
> PREEMPT".
> 

OK.  I have been able to test on a freshly installed CentOS 4.4 box
without RAID or LVM and I *do* see a great performance degradation when
bonnie++ is "writing intelligently". (I'm not sure it is as bad as what
I'm seeing on the raid1+lvm2 box, but it is definitely in the ballpark.)

This box is using a plain old PATA drive.

So, it's not RAID or LVM2 causing the problem.  The fact that the FC5
box, which is an old celeron 2GHz box with 512MB, does not exhibit the
problem indicates that it is not the CFQ scheduler causing the problem.

So does 2.6.9 just suck for heavy write IO?

-Steve