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Re: quotacheck speed

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: quotacheck speed
From: Arkadiusz Miśkiewicz <arekm@xxxxxxxx>
Date: Mon, 13 Feb 2012 19:09:50 +0100
Cc: xfs@xxxxxxxxxxx
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On Monday 13 of February 2012, Christoph Hellwig wrote:
> On Sun, Feb 12, 2012 at 10:01:07PM +0100, Arkadiusz Mi??kiewicz wrote:
> > Hi,
> > 
> > When mounting 800GB filesystem (after repair for example) here quotacheck
> > takes 10 minutes. Quite long time that adds to whole time of filesystem
> > downtime (repair + quotacheck).
> > 
> > I wonder if quotacheck can be somehow improved or done differently like
> > doing it in parallel with normal fs usage (so there will be no downtime)
> > ?
> I think the best idea to improve the performance in case you did a
> repair is to integrate the quotacheck code into repair.  It's fairly
> simple given that quotacheck simply walks all inodes and adds their
> space usage to the correct user/group/project, and given that repair
> already walks all inodes, and checks their block maps it does most of
> that work already.

That would be interesting and probably make 

> The only downside would be that the memory usage
> of repair increases a bit by keeping the dquots in memoryb, but even
> for your 130000 dquot setup that would add about 100 bytes * 130000
> please a bit of in-memory metadata (less than 20MB total) of memory
> usage, so it probably is a good tradeoff.

> In what cases do you regularly run quotacheck when you did not do
> a repair first?

I don't initiate quotacheck manually. AFAIK internal xfs quotacheck happens in 
two cases here:
1) repair->mount
2) filesystem has quotacheck done properly some time ago -> umount -> mount-
>oops/reset/something like that happens while mounting -> new mount

Arkadiusz Miśkiewicz        PLD/Linux Team
arekm / maven.pl            http://ftp.pld-linux.org/

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