linux-ext4 - Re: optimising filesystem for many small files

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Date:	Sat, 17 Oct 2009 09:32:57 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Viji V Nair <viji@...oraproject.org>
CC:	ext3-users@...hat.com, linux-ext4@...r.kernel.org
Subject: Re: optimising filesystem for many small files

Viji V Nair wrote:
> Hi,
> 
> System : Fedora 11 x86_64
> Current Filesystem: 150G ext4 (formatted with "-T small" option)
> Number of files: 50 Million, 1 to 30K png images
> 
> We are generating these files using a python programme and getting very 
> slow IO performance. While generation there in only write, no read. 
> After generation there is heavy read and no write.
> 
> I am looking for best practices/recommendation to get a better performance.
> 
> Any suggestions of the above are greatly appreciated.
> 
> Viji
> 

I would start with using blktrace and/or seekwatcher to see what your IO 
patterns look like when you're populating the disk; I would guess that 
you're seeing IO scattered all over.

How you are placing the files in subdirectories will affect this quite a 
lot; sitting in 1 directory for a while, filling with images, before 
moving on to the next directory, will probably help.  Putting each new 
file in a new subdirectory will probably give very bad results.

-Eric
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