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Re: file systems

Ron Johnson put forth on 4/25/2011 4:54 PM:
> On 04/25/2011 02:33 PM, Stan Hoeppner wrote:
>> Ron Johnson put forth on 4/25/2011 1:25 AM:
>>> On 04/19/2011 05:42 PM, Stan Hoeppner wrote:
>>> [snip]
>>>> XFS beats EXT4 hands down in nearly every category,
>>> Including not being able to xfs_check very large filesystems on 32 bit
>>> machines.  (Which if why I'm going back to ext4.)
>> This is an odd statement given that XFS (on 32 bit archs) and EXT4 both
>> currently top out at 16 TiB.  Thus moving to EXT4 gains you nothing on a
>> 32 bit machine, and you lose many advantages.
>> Please define "very large filesystems" and post the specific error
>> message you received when running xfs_check on this "very large
>> filesystem" on your 32 bit machine.
> The fs was approx 3.5TB.
> # xfs_check /dev/mapper/backup_vg-backup_lv
> xfs_check: Out Of Memory

This is not a 32 bit system limitation per se, as you initially claimed,
but a memory size limitation, as the error clearly states.  This is a
well known issue with xfs_check BTW, plenty of info available via your
favorite search engine, including workarounds.

Using 'xfs_repair -n' will give you essentially the same results as
xfs_check but with much less memory usage.  Assuming you have 4GB
physical RAM in the box in question 'xfs_repair -n' should work for a
3.5TB XFS.

Newer versions of xfs_check require less RAM than older versions, but
xfs_check still needs significant memory resources for checking large
filesystems with lots of inodes and lots of fragmented free space.

To address the 32 bit system limitation claim, running a PAE kernel with
xfsprogs apps compiled with PAE support will get around this out of
memory error, assuming you have enough physical RAM.  PAE supports up to
64GB.  I do not recommend this.  I'm simply stating it is possible.
Since most x86 chips shipped in the past 6 years support x86-64, you're
better off using a full 64 bit distro and a machine with 8GB or more RAM.


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