Re: optimising filesystem for many small files

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IMHO, software tuning will only yield incremental improvments. I suggest that you throw more and better hardware at the problem. And, as always, YMMV.

- Ken



----- Original Message ----- From: "Viji V Nair" <viji@xxxxxxxxxxxxxxxxx>
To: "Eric Sandeen" <sandeen@xxxxxxxxxx>
Cc: <linux-ext4@xxxxxxxxxxxxxxx>; <ext3-users@xxxxxxxxxx>
Sent: Saturday, October 17, 2009 1:56 PM
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@xxxxxxxxxx> 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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