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.
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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