linux-kernel - Re: unfair io behaviour for high load interactive use still present in 2.6.31

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Date:	Tue, 15 Sep 2009 04:02:10 -0700 (PDT)
From:	Daniel J Blueman <daniel.blueman@...il.com>
To:	Tobias Oetiker <tobi@...iker.ch>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: unfair io behaviour for high load interactive use still present 
	in 2.6.31

On Sep 15, 8:50 am, Tobias Oetiker <t...@...iker.ch> wrote:
> Experts,
>
> We run several busy NFS file servers with Areca HW Raid + LVM2 + ext3
>
> We find that the read bandwidth falls dramatically as well as the
> response times going up to several seconds as soon as the system
> comes under heavy write strain.

It's worthwhile checking:
 - that the ext3 filesystem starts at a stripe-aligned offset
 - that the ext3 filesystem was created with the correct stripe-width
and stride (chunk) size
 - due to the larger amount of memory, ext4 may be a big win (due to
delayed allocate), if you'll stay with a newer kernel
 - if you have battery backup at the right levels:
  - performance may be better mounting the ext3 filesystem with
'barrier=0'
  - performance may improve mounting 'data=writeback'

Thanks,
  Daniel
--
Daniel J Blueman
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