CentOS - Dec 2009 - Is ext4 safe for a production server?

I am about to install a new server running CentOS 5.4. The server will 
contain pretty critical data that we can't afford to corrupt.

I would like to benefit from the extra speed and features of a ext4 
filesystem but I don't have any experience with it.
Is there some member of the list who can enlighten me on whether ext4 is 
mature enough to be used on a production server without too much risk?

Thank you!

Miguel Medalha wrote:
> I am about to install a new server running CentOS 5.4. The server will 
> contain pretty critical data that we can't afford to corrupt.
>
> I would like to benefit from the extra speed and features of a ext4 
> filesystem but I don't have any experience with it.
> Is there some member of the list who can enlighten me on whether ext4 is 
> mature enough to be used on a production server without too much risk?
>
>   
Some people have encountered data loss issues on Ubuntu (quite some time 
back and nothing reported recently) and ext4 support is not yet official 
in Centos5/RHEL5.

Miguel Medalha wrote:
>> (...) The xfs kernel module offered by CentOS
>> became kABI-compatible sometime ago -- meaning it survives kernel
>> updates.
> 
> That is a clear improvement over the previous situation. I did suspect 
> it but was not sure about it. Thank you for the information. I will do 
> some tests with xfs, then.
> 
>> And, as of CentOS 5.4, xfs is now enabled in the kernel, so
>> no need for any external kernel module. But yes, this is available for
>> x86_64 only
> 
> ... a decision that many people have trouble at understanding!
It seems like a logical choice, given that xfs tends to crash with the 4k stacks
in the 32 bit kernel especially when layered with lvm/md/nfs.

-- 
   Les Mikesell
    lesmikesell at gmail.com

On Sat, Dec 5, 2009 at 10:20 AM, Miguel Medalha <miguelmedalha at sapo.pt>
wrote:
> I am about to install a new server running CentOS 5.4. The server will
> contain pretty critical data that we can't afford to corrupt.
>
> I would like to benefit from the extra speed and features of a ext4
> filesystem but I don't have any experience with it.
> Is there some member of the list who can enlighten me on whether ext4 is
> mature enough to be used on a production server without too much risk?
>
> Thank you!
>
Regardless of the technical issues offered here, ask yourself this: Do
you really want to be experimenting with a new file system on a
production server with "pretty critical data"?  Since you asked about
"too much risk", I think you already answered the question.

Any sane process would involve installing it on a low priority test
server, running for a while to see how it goes, and learning about new
features or tools.  After you've done that on a few lower priority
servers, for maybe a year or so, then you might start to _think_ about
using it on a production server like this.

My guess is that any additional speed can come from tuning other areas
of your server and disk subsystem.  What hardware do you have?  What
kind of disks?  Using RAID?  What level?  Have you looked into
aligning your partitions with the RAID blocks?  I'm sure that some of
the hardcore disk I/O people on the list can ask better questions and
give more meaningful recommendations.

Miguel Medalha wrote:
> I am about to install a new server running CentOS 5.4. The server will 
> contain pretty critical data that we can't afford to corrupt.
> 
Just for the record, Theodore Ts'o marked ext4 as stable and ready for 
general usage more than one year ago [1]. On 25 December 2008 kernel 
2.6.28 was released with ext4 considered ready for production. So, ext4 
is not _that_ new anymore. One year latter that Fedora 12 and Ubuntu 
9.10 began using ext4 as default.

I believe for 5.5 or even on 5.6, ext4 will not be a tech preview 
anymore. Considering that RH has extended the support so much, and how 
ext3 is so limited with the current and future disk's capacities (fsck 
on a 1TB volume is not funny). The current ext4 module is close to the 
one on 2.6.29 plus lots of fixes [2]

[1] 
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=03010a3350301baac2154fa66de925ae2981b7e3
[2] rpm -q --changelog kernel|grep ext4