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Re: Number of ACLs

To: Laurent CARON <lcaron@xxxxxxxxx>
Subject: Re: Number of ACLs
From: Emmanuel Florac <eflorac@xxxxxxxxxxxxxx>
Date: Thu, 7 Jul 2011 15:20:59 +0200
Cc: xfs@xxxxxxxxxxx
In-reply-to: <4E15AA1A.3090802@xxxxxxxxx>
Organization: Intellique
References: <4E15AA1A.3090802@xxxxxxxxx>
Le Thu, 07 Jul 2011 14:44:10 +0200
Laurent CARON <lcaron@xxxxxxxxx> écrivait:

> I'd like to know if it is possible in a simple & safe way to increase 
> the number of supported ACLs on an already existing FS.
> 
> xfs_acl.h:
> #define XFS_ACL_MAX_ENTRIES 25
> 
> Changing XFS_ACL_MAX_ENTRIES to something higher should do the trick, 
> but will it be safe: ie: will I risk corrupting the FS this way ?
> 
> I understand it'll imply a performance penalty if I add too many ACLs.

I asked recently to the list if there was any evolution on this point,
but unfortunately my question went ignored :( 

Actually you can't simply change this entry and hope that it will
work;  from what I understood, at best your filesystem will become
incompatible with any other kernel in the best case and you may need
to recompile the xfs tools too; in the worst case, compilation will
simply fail.

If you really need a lot of ACLs, the best answer so far is to use JFS,
which supports 1024 ACLs per file without tinkering and without pain.
The main culprit with JFS lies in relatively poor ageing (compared to
XFS), and no available tool to contain fragmentation. Imperfect world.

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