From: Goffredo Baroncelli <krexxjack@libero.it>
To: Liu Bo <liubo2009@cn.fujitsu.com>
Cc: "Matthias G. Eckermann" <mge@suse.com>, Alex <alex@bpmit.com>,
linux-btrfs@vger.kernel.org
Subject: Re: Create subvolume from a directory?
Date: Wed, 28 Mar 2012 18:54:40 +0200 [thread overview]
Message-ID: <4F734250.5030009@libero.it> (raw)
In-Reply-To: <4F727504.3070105@cn.fujitsu.com>
Hello Liu
On 03/28/2012 04:18 AM, Liu Bo wrote:
> On 03/28/2012 06:24 AM, Matthias G. Eckermann wrote:
>> # time cp -a --reflink /var/lib/lxc/installserver_tmp/rootfs /var/lib/lxc/installserver
>>
>
> This is too much weird.
>
> AFAIK, clone between different subvolumes should be forbidden.
> So this would get a "Invalid cross-device link", because an individual subvolume can be mounted directly.
Could you elaborate which would be the issue ?
"cp --reflink"-ing a file is not different than snapshotting a file. In
any case I could mount a snapshot and not the source subvolume.
>
> thanks,
> liubo
>
>> real 0m1.367s
>> user 0m0.148s
>> sys 0m1.108s
>>
>> ## Now remove /var/lib/lxc/installserver_tmp (or not)
>>
>> ------------------------------< snap>------------------------------
>>
>> Just to compare this with a "mv":
>>
>> ------------------------------< snip>------------------------------
>>
>> ## Go back to former state
>>
>> # btrfs subvol delete /var/lib/lxc/installserver
>> Delete subvolume '/var/lib/lxc/installserver'
>>
>> # btrfs subvol create /var/lib/lxc/installserver
>> Create subvolume '/var/lib/lxc/installserver'
>>
>> # time mv /var/lib/lxc/installserver_tmp/rootfs /var/lib/lxc/installserver/
>>
>> real 0m12.917s
>> user 0m0.208s
>> sys 0m2.508s
>>
>> ------------------------------< snap>------------------------------
>>
>> While the time measurement might be flawed due to the subvol
>> actions inbetween, caching etc.: I tried several times, and
>> "cp --reflinks" always is multiple times faster than "mv" in
>> my environment.
>>
>> Or did I misunderstand your question?
>>
>> so long -
>> MgE
>>
>
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>
next prev parent reply other threads:[~2012-03-28 16:54 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-27 17:19 Create subvolume from a directory? Alex
2012-03-27 20:42 ` Chester
2012-03-27 22:24 ` Matthias G. Eckermann
2012-03-28 1:46 ` Fajar A. Nugraha
2012-03-28 9:20 ` David Sterba
2012-03-28 2:18 ` Liu Bo
2012-03-28 16:54 ` Goffredo Baroncelli [this message]
2012-03-29 1:24 ` Liu Bo
2012-05-01 17:09 ` Hubert Kario
2012-05-02 16:33 ` David Sterba
2012-05-03 13:26 ` Hubert Kario
2012-05-14 12:36 ` David Sterba
2012-03-28 9:24 ` David Sterba
2012-03-28 11:11 ` Alex
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