From: Eric Sandeen <sandeen@sandeen.net>
To: Spelic <spelic@shiftmail.org>, xfs@oss.sgi.com
Subject: Re: XFS shrinking planned?
Date: Wed, 29 Oct 2014 08:03:07 -0500 [thread overview]
Message-ID: <5450E58B.10106@sandeen.net> (raw)
In-Reply-To: <5450B560.6000208@shiftmail.org>
On 10/29/14 4:37 AM, Spelic wrote:
> 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.
"probably"
> Then using thinp would mess up
> all the disk layout, basically replacing the XFS allocator, which
> most likely would decrease performances significantly.
"most likely"
> 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.
"presumably"
> All this would result in a performance almost certainly
> lower than ext4.
"almost certainly..."
All possibilities, but possibly also worth testing to find out. ;)
It's true that today the thinp allocator will impact XFS allocation
patterns to some degree.
Anyway, shrink has been on the radar for years, it's just never really
been a priority. It might happen some day...
-Eric
> Thanks
> S.
>
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prev parent reply other threads:[~2014-10-29 13:03 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-28 16:19 XFS shrinking planned? Spelic
2014-10-28 17:39 ` Eric Sandeen
2014-10-29 9:37 ` Spelic
2014-10-29 13:03 ` Eric Sandeen [this message]
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