Mailstore filesystem

Simon Matter simon.matter at
Wed Jul 5 12:37:34 EDT 2006

> Hello,
>> How big?  ext3 STILL only supports 32000 directories within a directory.
>> That gets to be quite a problem on large installs.
> it is true: Performance goes down on very large directories with ext3.
> But these cases should be very rare. How often would it happen to store
> millions of files within on directory?
> And ext3 unfortunately really only allows 32000 subdirectories (only
> 31998 to be exactly, because . and .. are counted as well). I hope this
> will be improvent on newer releases.

Yes, you don't need alot of subdirs only because most software needing it
implements all those hacks called dirhashing. It's to compensate those
filesystems limitations of ancient filesystems.

> However, Redhat ships with only one filesystem: ext3. And their kernel
> doesn't support anything else (speaking of rhel4, with rhel3 you could
> optionally load modules to support reiserfs and some other filesystems
> but root partition had to be ext3).

That's unfortunately true, but the nice CentOS people provide XFS enabled
RH kernels. I'm using XFS on RedHat EL4U3 for filesystems where ext3 just
doesn't handle it. For example it's a backupserver which mainly holds
backups of a large number of servers using rsnapshot. ext3 just didn't
handle the large number of files, directories and hardlinks. After a long
time of crashes and completely broken filesystems, I decided to go once
again with XFS. The volume was remormatted with XFS and since then handles
it with hundred of millions of files, directories and hardlinks without
any problem. Of course that may be a very special case and if it's a cyrus
server of that size, most people would want to split the filesystem. But,
there are situations where RedHat's preferred ext3 just doesn't handle it.


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