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From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Gionatan Danti <g.danti@assyoma.it>
Cc: linux-xfs@vger.kernel.org
Subject: Re: XFS reflink vs ThinLVM
Date: Sat, 18 Jan 2020 15:06:31 -0800	[thread overview]
Message-ID: <20200118230631.GX8247@magnolia> (raw)
In-Reply-To: <cc3d0819966d2d3f5b8512ed0f6b1de1@assyoma.it>

On Sat, Jan 18, 2020 at 12:08:48PM +0100, Gionatan Danti wrote:
> Il 18-01-2020 00:42 Darrick J. Wong ha scritto:
> > How many fragments, and how big of a sparse file?
> 
> A just installed CentOS 8 guest using a 20 GB sparse file vdisk had about
> 2000 fragments.
> 
> After running "fio --name=test --filename=test.img --rw=randwrite --size=4G"

4GB / 1M extents == 4096, which is probably the fs blocksize :)

I wonder, do you get different results if you set an extent size hint
on the dir before running fio?

I forgot(?) to mention that if you're mostly dealing with sparse VM
images then you might as well set a extent size hint and forego delayed
allocation because it won't help you much.

--D

> for about 30 mins, it ended with over 1M fragments/extents. At that point,
> reflinking that file took over 2 mins, and unlinking it about 4 mins.
> 
> I understand fio randwrite pattern is a worst case scenario; still, I think
> the results are interesting and telling for "aged" virtual machines.
> 
> As a side note, a just installed Win2019 guest backed with an 80 GB sparse
> file had about 18000 fragments.
> Thanks.
> 
> -- 
> Danti Gionatan
> Supporto Tecnico
> Assyoma S.r.l. - www.assyoma.it
> email: g.danti@assyoma.it - info@assyoma.it
> GPG public key ID: FF5F32A8

  reply	other threads:[~2020-01-18 23:06 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-13 10:22 XFS reflink vs ThinLVM Gionatan Danti
2020-01-13 11:10 ` Carlos Maiolino
2020-01-13 11:25   ` Gionatan Danti
2020-01-13 11:43     ` Carlos Maiolino
2020-01-13 12:21       ` Gionatan Danti
2020-01-13 15:34         ` Gionatan Danti
2020-01-13 16:53           ` Darrick J. Wong
2020-01-13 17:00             ` Gionatan Danti
2020-01-13 18:09               ` Darrick J. Wong
2020-01-14  8:45                 ` Gionatan Danti
2020-01-15 11:37                   ` Gionatan Danti
2020-01-15 16:39                     ` Darrick J. Wong
2020-01-15 17:45                       ` Gionatan Danti
2020-01-17 21:58                         ` Gionatan Danti
2020-01-17 23:42                           ` Darrick J. Wong
2020-01-18 11:08                             ` Gionatan Danti
2020-01-18 23:06                               ` Darrick J. Wong [this message]
2020-01-19  8:45                                 ` Gionatan Danti
2020-01-13 16:14 ` Chris Murphy
2020-01-13 16:25   ` Gionatan Danti

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