To: Tomasz Chmielewski <mangoo@wpkg.org>
Cc: LKML <linux-fsdevel@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: very poor ext3 write performance on big filesystems?
From: Andi Kleen <andi@firstfloor.org>
References: <47B980AC.2080806@wpkg.org>
Date: Mon, 18 Feb 2008 15:03:44 +0100
In-Reply-To: <47B980AC.2080806@wpkg.org> (Tomasz Chmielewski's message of "Mon\, 18 Feb 2008 13\:57\:16 +0100")
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Tomasz Chmielewski <mangoo@wpkg.org> writes:
>
> Is it normal to expect the write speed go down to only few dozens of
> kilobytes/s? Is it because of that many seeks? Can it be somehow
> optimized? 

I have similar problems on my linux source partition which also
has a lot of hard linked files (although probably not quite
as many as you do). It seems like hard linking prevents
some of the heuristics ext* uses to generate non fragmented
disk layouts and the resulting seeking makes things slow.

What has helped a bit was to recreate the file system with -O^dir_index
dir_index seems to cause more seeks.

Also keeping enough free space is also a good idea because that
allows the file system code better choices on where to place data.

-Andi

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