what is the FS size limit for xfs_repair ?

what is the FS size limit for xfs_repair ?

[Emmanuel Florac]

After a system crash on a system with a 40TB XFS filesystem, xfs_repair
(32 bits binary, with a 64 bits 2.6.24 kernel) refused to work ("cannot
allocate block map, size xxx").
The 64 bits xfs_repair did the trick fine. 

I tried to reproduce the problem today by corrupting a 22TB filesystem.
However, 32 bits xfs_repair repaired the 22 TB FS just fine in the very
same configuration (64 bits kernel, etc).

I thought the limit would be at 16TB (32 bits limit for a filesystem)
but obviously this isn't the case. Is the limitation higher (like 32
TB) or is it a bug of etch 4.0r4 xfs_repair?

-- 
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Emmanuel Florac     |   Intellique
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Re: what is the FS size limit for xfs_repair ?

[James Braid]

2008/10/3 Emmanuel Florac <eflorac@intellique.com>:
> I thought the limit would be at 16TB (32 bits limit for a filesystem)
> but obviously this isn't the case. Is the limitation higher (like 32
> TB) or is it a bug of etch 4.0r4 xfs_repair?

The limit is how much memory a 32-bit process can allocate - it's not
a limit of xfs_repair itself.

xfs_repair uses different amounts of memory depending on the
filesystem characteristics (number of inodes etc) - so a 32-bit
xfs_repair might work fine on an empty filesystem but not on a
filesystem with loads of files on it. e.g. we had a ~2TB filesystem
with millions of inodes and 32-bit xfs_repair failed.

Re: what is the FS size limit for xfs_repair ?

[Emmanuel Florac]

Le Fri, 3 Oct 2008 16:23:41 +0100 vous écriviez:

> The limit is how much memory a 32-bit process can allocate - it's not
> a limit of xfs_repair itself.

OK, that makes sense. I'll keep my 64 bits xfs_repair at hand :)

-- 
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Emmanuel Florac               www.intellique.com   
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Re: what is the FS size limit for xfs_repair ?

[Mark Goodwin]

Emmanuel Florac wrote:
> Le Fri, 3 Oct 2008 16:23:41 +0100 vous écriviez:
> 
>> The limit is how much memory a 32-bit process can allocate - it's not
>> a limit of xfs_repair itself.
> 
> OK, that makes sense. I'll keep my 64 bits xfs_repair at hand :)
> 

As a rule of thumb with a fairly recent xfs_repair, you need approx
128MB RAM per TB filesystem size (but it also depends on number of
inodes too).

Cheers
-- Mark