From: Josef Bacik <jbacik@fb.com>
To: Kai Krakow <hurikhan77+btrfs@gmail.com>, <linux-btrfs@vger.kernel.org>
Subject: Re: Are nocow files snapshot-aware
Date: Tue, 4 Feb 2014 20:22:05 -0500 [thread overview]
Message-ID: <52F1923D.8090306@fb.com> (raw)
In-Reply-To: <mh08sa-5tp.ln1@hurikhan77.spdns.de>
On 02/04/2014 03:52 PM, Kai Krakow wrote:
> Hi!
>
> I'm curious... The whole snapshot thing on btrfs is based on its COW design.
> But you can make individual files and directory contents nocow by applying
> the C attribute on it using chattr. This is usually recommended for database
> files and VM images. So far, so good...
>
> But what happens to such files when they are part of a snapshot? Do they
> become duplicated during the snapshot? Do they become unshared (as a whole)
> when written to? Or when the the parent snapshot becomes deleted? Or maybe
> the nocow attribute is just ignored after a snapshot was taken?
>
> After all they are nocow and thus would be handled in another way when
> snapshotted.
>
When snapshotted nocow files fallback to normal cow behaviour. Thanks,
Josef
next prev parent reply other threads:[~2014-02-05 1:22 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-04 20:52 Are nocow files snapshot-aware Kai Krakow
2014-02-05 1:22 ` Josef Bacik [this message]
2014-02-05 2:02 ` David Sterba
2014-02-05 18:17 ` Kai Krakow
2014-02-06 2:38 ` Duncan
2014-02-07 0:32 ` Kai Krakow
2014-02-07 1:01 ` cwillu
2014-02-07 1:28 ` Chris Murphy
2014-02-07 21:07 ` Kai Krakow
2014-02-07 21:31 ` Chris Murphy
2014-02-07 22:26 ` Kai Krakow
2014-02-08 6:34 ` Duncan
2014-02-08 8:50 ` Kai Krakow
2014-02-07 7:06 ` Duncan
2014-02-07 21:58 ` Kai Krakow
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