Re: Cloning / getting a full backup of a BTRFS filesystem

From: Qu Wenruo <quwenruo.btrfs@gmx.com>
To: Anand Jain <anand.jain@oracle.com>,
	Chris Murphy <lists@colorremedies.com>
Cc: "Swâmi Petaramesh" <swami@petaramesh.org>,
	"Linux BTRFS Mailinglist" <linux-btrfs@vger.kernel.org>
Subject: Re: Cloning / getting a full backup of a BTRFS filesystem
Date: Thu, 5 Sep 2019 21:13:12 +0800	[thread overview]
Message-ID: <cb0a5e6e-ee0d-c62b-889a-a5e6c7cddc33@gmx.com> (raw)
In-Reply-To: <F4DE0ABD-51B3-4BBC-B26D-3599A78ED1E4@oracle.com>

On 2019/9/5 下午9:06, Anand Jain wrote:
>
>
>> On 5 Sep 2019, at 1:55 AM, Chris Murphy <lists@colorremedies.com> wrote:
>>
>> On Wed, Sep 4, 2019 at 12:16 AM Swâmi Petaramesh <swami@petaramesh.org> wrote:
>>>
>>> Hi list,
>>>
>>> Is there an advised way to completely “clone” a complete BTRFS
>>> filesystem, I mean to get an exact copy of a BTRFS filesystem including
>>> subvolumes (even readonly snapshots) and complete file attributes
>>> including extended attributes, ACLs and so, to another storage pool,
>>> possibly defined with a different RAID geometry or compression ?
>>
>
>  Remote replication is a planned feature, when ready, it can be
>  used with a local target to meet this requisite.

In fact, I have submitted patches to implement btrfs-image data dump
feature, which can be used here.
https://patchwork.kernel.org/project/linux-btrfs/list/?series=141937

Further more, since it's btrfs-image, it can even support cloning a
RAID5 fs into single device!
But I doubt btrfs-image -r would restore into another profile other the
original profile or single device.

Thanks,
Qu

>
>> The bottom line answer is no. There are only compromises.
>>
>> Btrfs seed sprout will do what you want, except you can't change
>> geometry or compression. Last time I tested multiple devices as either
>> a source or destination, I ran into problems - but it's possible some
>> of this has been fixed, which is a question for Anand Jain.
>
>  Thanks for the report. I just tested the below test case[1],
>  it does not fail. Any idea?
>
> [1]
>  Create and mount a two devices seed fs, and create a sprout.
>
>  umount /btrfs; mkfs.btrfs -fq -dsingle -msingle /dev/sdb /dev/sdc && mount /dev/sdb /btrfs && fillfs /btrfs 100 && umount /btrfs && btrfstune -S1 /dev/sdb && mount /dev/sdb /btrfs && btrfs dev add /dev/sdd /btrfs && umount /btrfs
>
>  Mount the sprout device and delete the seed devices to make
>  it an independent but identical fs.
>
>  mount /dev/sdd /btrfs && btrfs dev del /dev/sdb /btrfs && btrfs dev del /dev/sdc /btrfs
>
> Thanks, Anand
>
>
>
>
>