From: Liu Bo <bo.li.liu@oracle.com>
To: Fredrik Tolf <fredrik@dolda2000.com>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: Changing allocation mode
Date: Wed, 27 Feb 2013 09:28:33 +0800 [thread overview]
Message-ID: <20130227012832.GB7028@liubo> (raw)
In-Reply-To: <alpine.DEB.2.02.1302230138220.8295@shack.dolda2000.com>
On Sat, Feb 23, 2013 at 01:46:03AM +0100, Fredrik Tolf wrote:
> Dear list,
>
> I'm still in the process of transferring all the data I have to the
> btrfs filesystem I have had your help in debugging in a previous
> thread, and I have a slight question, if you will humour me.
>
> I have the data I want to transfer on an old ReiserFS partition,
> consisting of 2 mdraid mirrors, one of which consists of two 1.5 TB
> disks, and the other of two 3 TB disks. The btrfs I'm copying the
> data to consists of two 3 TB disks only that I have put in RAID-1
> mode, and the data on the old filesystem is only slightly larger
> than 3 TB. I am now at the point where I have transferred just under
> 3 TB.
>
> If I were transferring the data to a new filesystem on mdraid, the
> procedure I would use for that last portion of the data would be to
> remove one disk only from either of the old mdraid mirror arrays
> (putting that array in degraded mode), and then create a new mirror
> in degraded mode with only that disk, add that mirror to the new
> filesystem, expand it, copy the last data, and then delete the old
> mirrors, moving the rest of the disks to the new filesystem.
That sounds like using seed device, although seed disk is designed for another
different purpose.
thanks,
liubo
>
> Is there a way to mirror this procedure in btrfs? I'm not yet quite
> so familiar with all btrfs concepts that I know quite what I'm
> talking about, but I'm guessing that what I want to do is to merely
> temporarily set the allocator to allocate new btrfs on a single disk
> only, and then add a single disk to the filesystem. And then copy
> the rest of the data, abandon the old filesystem and add another
> disk and rebalance those singly-allocated extents to RAID-1 mode.
>
> Have I described a conceptionable idea in saying so? And if so, how
> does one actually do that? I don't know if I'm just blind, but I
> haven't found any btrfs command to change the allocation algorithm
> without having to rebalance the existing data, which seems a bit
> unnecessary in this case.
>
> Thanks for any help you can offer!
>
> --
>
> Fredrik Tolf
> --
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next prev parent reply other threads:[~2013-02-27 1:30 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-23 0:46 Changing allocation mode Fredrik Tolf
2013-02-27 1:28 ` Liu Bo [this message]
2013-03-02 0:45 ` Fredrik Tolf
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