Re: Help to know the stable ver of ext4 for commercial app.

[Theodore Ts'o <tytso@mit.edu>]

On Sat, Feb 02, 2013 at 02:30:11AM +0000, Wuqixuan wrote:
> 
>    Currently we are choocing ssd/sata file system using for stream media application. We are using 2.6.34.10 (can be upgraded to 2.6.34.14). We are consider of ext3 or ext4.  Even in wikipedia, it mentions ext4 is stable from 2.6.28, I still have some doubts: 
>  
>     1. Whether 2.6.34.10 of ext4 is stable enough for commercial use or not. 
>     2. Are there many mature commercial application on ext4 on 2.6.34.10 or before? Can tell some famous company or app name ? 

Well, it's _possible_ to use 2.6.34 as a base for a production server.
Red Hat's RHEL 5 was based on kernel of approximately that vintage
(with many, many patches).  Google announced it was upgrading its data
centers to use ext4 just about the time I was hired at Google[1], in
January 2010, and 2.6.34 dates from May 2010.

[1] http://lists.openwall.net/linux-ext4/2010/01/04/8

The team at Taobao was using a similar vintage kernel if I recall
correctly, at least at one point in time.  I'm not sure if they have
since upgraded to a newer kernel.

However, at Google, we used a huge number of patches to fix and
stablize ext4.  The patches were pushed upstream over a 18 months or
so, but not all of them were backported into 2.6.34.x kernels.  I
believe you will find the same story at Red Hat and at Tao Bao.


Part of that is because the stable kernel maintainers will generally
just drop a patch if it doesn't apply cleanly.  In order to determine
which patches are applicable, and to adopt and backport patches, you
really will need one or more ext4 developers on staff, such as Eric
Sandeen and his colleagues for Red Hat, or me and my colleages for
Google, or Tao Ma and his team at Taobao.

Whether or not it's good enough for your streaming media application
is a different question.  That's a very restricted use case, and it
might be good enough.   You should test it and see for yourself.  

Regards,

						- Ted