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

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Date:	Sat, 17 Oct 2009 23:26:04 +0530
From:	Viji V Nair <viji@...oraproject.org>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	ext3-users@...hat.com, linux-ext4@...r.kernel.org
Subject: Re: optimising filesystem for many small files

these files are not in a single directory, this is a pyramid
structure. There are total 15 pyramids and coming down from top to
bottom the sub directories and files  are multiplied by a factor of 4.

The IO is scattered all over!!!! and this is a single disk file system.

Since the python application is creating files, it is creating
multiple files to multiple sub directories at a time.

On Sat, Oct 17, 2009 at 8:02 PM, Eric Sandeen <sandeen@...hat.com> wrote:
> 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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