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Re: XFS shrinking planned?

To: Eric Sandeen <sandeen@xxxxxxxxxxx>, Spelic <spelic@xxxxxxxxxxxxx>, xfs@xxxxxxxxxxx
Subject: Re: XFS shrinking planned?
From: Spelic <spelic@xxxxxxxxxxxxx>
Date: Wed, 29 Oct 2014 10:37:36 +0100
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On 28/10/2014 18:39, Eric Sandeen wrote:
Not formally planned, there are bits and pieces out there (i.e. the inode
mover) which are part of what it might take to achieve a shrinker.

Another option, rather than fs shrinking, is to use the dm-thinp target, which
would allow you to allocate a large-but-sparse block device, create a very
large filesystem on that, and add or remove storage as needed.
(At least I think you can remove it...!)

-Eric

Thanks for your reply Eric

Interesting technique, but for enforcing a maximum size (smaller than the very large allocated thin device) I would have to rely on quotas, which probably decreases performance. Then using thinp would mess up all the disk layout, basically replacing the XFS allocator, which most likely would decrease performances significantly. And then the thinp code itself is a medium performance thing and I don't think it can keep up with XFS performances, so that would presumably be a hard bottleneck.
All this would result in a performance almost certainly lower than ext4.

Thanks
S.

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