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tim at icukhosting

Oct 14, 2009, 9:45 AM

Post #1 of 5 (1153 views)
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Ext4

Hi List,

Does anyone have any experience with ext4? I'm in the process of putting
together some plans for a 2TB, RAID 10 backed, 2 node DRBD cluster to
run an NFS based file server, and I'm trying decide whether to stick
with ext3 or take the plunge into the world of ext4. The file server
will be the backend for a cluster of mail servers.

Any advice would be appreciated.


Thanks,
Tim

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diego.remolina at physics

Oct 14, 2009, 10:06 AM

Post #2 of 5 (1101 views)
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Re: Ext4 [In reply to]

I was using it without any issues on RHEL5.3 on two drbd volumes. The
first one was 12TB, the second 4TB.

I had no issues whatsoever related to drbd and the file system. I rolled
back to ext3 on my file systems when I found what turned out to be an
NFS bug in the 5.4 release kernel, where the permissions and times for
new files were getting screwed up very badly.

I originally thought that ext4 was at fault (being a Tech preview in
RHEL5.3), then asked the list if it could be a drbd issue, but in the
end the kernel that came with 5.4 was at fault.

The only issues I saw with the ext4 code on the 5.3 RHEL kernels was
that it had issues deleting files (this is independent of drbd). With
the new 5.4 kernels (where ext4 is based on a much fresher ext4 kernel
code) the issues were gone.

The benchmarks for ext4 over ext3 and the ability to run fsck without
having to check all empty space where the deciding factors for me
originally until I decided to revert back to ext3 for the sake of using
the proven file system (which I regret a bit now that my system is in
production, but I can change again on a long weekend). If you use a
distro which runs an even newer kernel (as compared to RHEL 5.x), you
will most likely have a very stable ext4 file system.

In case anybody hits the nfs kernel bug for RHEL5.4, here is the
bugzilla entry (ranting included ;):

https://bugzilla.redhat.com/show_bug.cgi?id=524520

Diego

Tim O'Donovan wrote:
> Hi List,
>
> Does anyone have any experience with ext4? I'm in the process of putting
> together some plans for a 2TB, RAID 10 backed, 2 node DRBD cluster to
> run an NFS based file server, and I'm trying decide whether to stick
> with ext3 or take the plunge into the world of ext4. The file server
> will be the backend for a cluster of mail servers.
>
> Any advice would be appreciated.
>
>
> Thanks,
> Tim
>
> _______________________________________________
> drbd-user mailing list
> drbd-user [at] lists
> http://lists.linbit.com/mailman/listinfo/drbd-user
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mcetra at navynet

Oct 14, 2009, 10:07 AM

Post #3 of 5 (1097 views)
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Re: Ext4 [In reply to]

Tim O'Donovan ha scritto:
> Hi List,
>
> Does anyone have any experience with ext4? I'm in the process of putting
> together some plans for a 2TB, RAID 10 backed, 2 node DRBD cluster to
> run an NFS based file server, and I'm trying decide whether to stick
> with ext3 or take the plunge into the world of ext4. The file server
> will be the backend for a cluster of mail servers.
>
> Any advice would be appreciated.
>
They say a lot of good things about ext4 performance.
But lurking into the linux kernel mailing list, i would suggest to wait
a bit more to use ext4 into production systems.

Max

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chibi at gol

Oct 14, 2009, 7:49 PM

Post #4 of 5 (1099 views)
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Re: Ext4 [In reply to]

On Wed, 14 Oct 2009 17:45:59 +0100 Tim O'Donovan wrote:
>
> Does anyone have any experience with ext4? I'm in the process of putting
> together some plans for a 2TB, RAID 10 backed, 2 node DRBD cluster to
> run an NFS based file server, and I'm trying decide whether to stick
> with ext3 or take the plunge into the world of ext4. The file server
> will be the backend for a cluster of mail servers.
>
I would guess that your biggest impact on performance will NFS and not the
underlying file system on the server.
That said, all the literature on ext4 looked good. Alas real life tests on
the same hardware with a 2.6.30 kernel delivered worse results (bonnie,
wall time, postmark) across the board for ext4 compared to ext3.
The lower create/delete rates for files would be of particular impact for
a mail (maildir at least) storage. Ultimately just test things on your
actual hardware to determine what is best for you.
I'm just phasing in a new mail storage cluster (no NFS) and while ReiserFS
is still the best (by design) FS for a maildir storage (the current mail
storage cluster uses reiser3) the uncertain future of it and the raw
performance numbers made me choose ext3.

In a year or 2 the best choice will likely be btrfs, but that is not here
nor now.

Regards,

Christian
--
Christian Balzer Network/Systems Engineer
chibi [at] gol Global OnLine Japan/Fusion Communications
http://www.gol.com/
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tim at icukhosting

Oct 16, 2009, 6:01 AM

Post #5 of 5 (1084 views)
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Re: Ext4 [In reply to]

Many thanks for all the advice and suggestions folks, much appreciated.
As much as I would love to use ext4, after reviewing everything and
weighing up the pros and cons, I think it's probably wiser to stick with
the tried and tested stability of ext3. Faster fscking alone does make
ext4 very tempting, but it looks like it might be a while before it's
guaranteed to be as reliable as ext3. Will probably revisit this on the
next upgrade in a couple of years, but as Christian pointed out, btrfs
may be the way to go by then.

Thanks again.

Tim
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