Date: Thu, 24 Jan 2008 12:26:34 +1100
To: "David Chinner" <dgc@sgi.com>, "Ralf Gross" <Ralf-Lists@ralfgross.de>
Subject: Re: xfs_rapair memory requirement per TB
From: "Barry Naujok" <bnaujok@sgi.com>
Organization: SGI
Cc: xfs@oss.sgi.com
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On Thu, 24 Jan 2008 11:28:28 +1100, David Chinner <dgc@sgi.com> wrote:

> On Wed, Jan 23, 2008 at 09:53:39AM +0100, Ralf Gross wrote:
>> Barry Naujok schrieb:
>> > >
>> > >Reading the "Repairing a possibly incomplete xfs_growfs command?"  
>> thread
>> > >this month makes me wonder if there is some type of rough formula or
>> > >guesstimation cheat sheet to figure out how much memory and swap one
>> > >would need for an xfs_repair given a file system with many terabytes.
>> > >
>> > >
>> > >Say I have an 8TB LUN that needs an xfs_repair.  What would be the  
>> rough
>> > >memory requirements and swap space?
>> > >
>> >
>> > General rule of thumb at the moment is 128MB of RAM/TB of filesystem
>> > plus 4MB/million inodes on that filesystem.
>>
>> Did this change lately? I found the rule of thumb: 2 GB RAM for 1 TB
>> of disk storage + some RAM per x inodes.
>
> The above is based on actual theoretical usage, the below:
>
>> http://oss.sgi.com/archives/xfs/2005-08/msg00045.html
>
> was based on reported usage on during live repair runs.
>
> I think Barry discovered the difference to be things external
> to repair such as heap fragmentation and has since corrected
> the worst of the issues so requirements are, in general,
> much closer to the theoretical numbers now.

Yes, quite a few memory improvements have been made.

Right now, I can repair a 9TB filesystem with ~150 million inodes
in 2GB of RAM without going to swap using xfs_repair 2.9.4 and
with no custom/tuning/config options.

Regards,
Barry.