linux-kernel - Re: very poor ext3 write performance on big filesystems?

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Date:	Mon, 18 Feb 2008 15:03:44 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Tomasz Chmielewski <mangoo@...g.org>
Cc:	LKML <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: very poor ext3 write performance on big filesystems?

Tomasz Chmielewski <mangoo@...g.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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