From: Dave Chinner <david@fromorbit.com>
To: Gionatan Danti <g.danti@assyoma.it>
Cc: linux-xfs@vger.kernel.org
Subject: Re: Reflink (cow) copy of busy files
Date: Sun, 25 Feb 2018 09:07:57 +1100 [thread overview]
Message-ID: <20180224220757.GC30854@dastard> (raw)
In-Reply-To: <9e69fcd01e1c02ea53e0e1ac66d60d24@assyoma.it>
On Sat, Feb 24, 2018 at 07:20:48PM +0100, Gionatan Danti wrote:
> Hi all,
> I have a question on how CoW/reflink works when used on busy files,
> as vm image files, databases, ecc.
Define "busy file", please.
> In short: can reflink-copy be used to create a crash-consistent
> snapshot of, say, a busy vm disk file?
If the file is being actively written, then the clone will not be
consistent.
> Or the db/vm/whatever should
> be quiesced before taking the copy (ie: similarly to how lvm call
> fsfreeze during the snapshot)?
Yes, it's just like any other snapshot process - you have to quiesce
everything that is writing to the file before cloning it. i.e. the
data in the file needs to be in a stable, consistent, unchanging
state if you want the clone to contain consistent data...
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2018-02-24 22:07 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-24 18:20 Reflink (cow) copy of busy files Gionatan Danti
2018-02-24 22:07 ` Dave Chinner [this message]
2018-02-24 22:57 ` Gionatan Danti
2018-02-25 2:47 ` Dave Chinner
2018-02-25 11:40 ` Gionatan Danti
2018-02-25 21:13 ` Dave Chinner
2018-02-25 21:58 ` Gionatan Danti
2018-02-26 0:25 ` Dave Chinner
2018-02-26 7:19 ` Gionatan Danti
2018-02-26 7:58 ` Amir Goldstein
2018-02-26 8:26 ` Gionatan Danti
2018-02-26 17:26 ` Darrick J. Wong
2018-02-26 21:23 ` Gionatan Danti
2018-02-26 21:31 ` Darrick J. Wong
2018-02-26 21:39 ` Gionatan Danti
2018-02-27 0:33 ` Dave Chinner
2018-02-27 0:58 ` Darrick J. Wong
2018-02-27 8:06 ` Gionatan Danti
2018-02-27 22:04 ` Dave Chinner
2018-02-28 7:08 ` Gionatan Danti
2018-02-28 17:07 ` Darrick J. Wong
2018-02-28 18:27 ` Gionatan Danti
2018-02-26 20:29 ` Amir Goldstein
2018-02-26 21:28 ` Gionatan Danti
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