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OpenSuse 13.2 with a default BTRFS file system is now out; however,
I always wait a while before trying a new version so as to give the
developers time to sort out the usual rush of new bugs that did not
show up during beta testing. In the meantime I decided to try out
BTRFS on my existing OpenSuse 13.1 installation but without a
complete conversion. I have therefore just converted my data
partition which resides on my SSD and mirror it with BTRFS RAID1 on
my HD. My SSD is just 240 GB, my HD is 1 TB and my data partition is
150 GB. This partition excludes photos and video since there is no
room for those on my SSD and I access those infrequently compared to
the stuff on my 150 GB data partition. Photos and Videos are in a
partition on the 1 TB HD.<br>
<br>
My test then was on 150 GB SSD (sdb7) and 150 GB HD(sda9), mirrored
with RAID 1. There are lots of articles and documents to view on
BTRFS and quoting from one:<br>
<br>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<span style="color: rgb(51, 51, 51); font-family: Arial, Helvetica,
sans-serif; font-size: 12px; font-style: normal; font-variant:
normal; font-weight: normal; letter-spacing: normal; line-height:
18px; orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; display: inline
!important; float: none; background-color: rgb(255, 255, 255);">"The
RAID in Btrfs has some differences from the old-fashioned RAID
we're used to. In Btrfs RAID0 stripes your data across all
available devices with no redundancy. RAID1 mirrors your data in
pairs, round-robin across all available devices, so there are
always two copies of your metadata regardless of how many devices
are in the storage pool.</span>"<br>
<br>
So I could set up RAID 1 with mirrored meta data or with everything
mirrored. I chose the latter. Before starting of course I made a
fresh backup of my data (sdb7) and then tried:<br>
<br>
# btrfs-convert /dev/sdb7<br>
<br>
it seemed to work in that I could mount it and access it but when I
tried to add a second drive (sda9) and convert it to RAID 1 it
failed. eg<br>
<br>
# mount /dev/sdb7 /mnt/btrfs-test/<br>
# btrfs device add -f /dev/sda9 /mnt/btrfs-test/<br>
# btrfs balance start -dconvert=raid1 -mconvert=raid1
/mnt/btrfs-test/<br>
# "failed - error message", it didn't matter whether of not sda9 was
formatted ext4 or btrfs. <br>
<br>
Since I had a fresh backup of sdb7 I decided to reformat both sdb7
and sda9 and build a RAID 1 btrfs pair from scratch, I had already
tried this out on a spare USB HD so I new it would work i.e.<br>
<br>
# mkfs.btrfs -f -d raid1 /dev/sdb7 /dev/sda9<br>
# btrfs filesystem label /dev/sdb7 DATA (I could have used
the -L option in the above command to do this)<br>
# mount /dev/sdb7 /home/john/data<br>
<br>
To see what has been done:<br>
# btrfs filesystem show <br>
<br>
Finally it was necessary to update my /etc/fstab file which used to
contain the mounting instruction:<br>
<br>
/dev/sdb7 /home/john/data ext4
defaults,user_xattr 0 0<br>
<br>
and change to:<br>
<br>
/dev/sdb7 /home/john/data btrfs
device=/dev/sdb7,device=/dev/sda9,defaults 0 0<br>
<br>
after saving /etc/fstab and unmounting;<br>
<br>
# umount /dev/sdb7<br>
<br>
and then re-mount:<br>
<br>
# mount -a<br>
<br>
SUCCESS!<br>
<br>
One more thing to note is that gparted shows a warning error on sdb7
plus the normal mounted symbol (a key) and no used space info,
whereas, sda9 shows no mounted symbol and the correct used space
info. Also the normal commands df and du do not work correctly for
BTRFS you need to use:<br>
<br>
# btrfs filesystem df /home/john/data/<br>
<br>
I shall still of course be running my regular daily and weekly
backups since this is all automatic and unaffected by the change.
Hopefully I will learn over the course of the coming weeks whether
or not there are any problems with this setup and if I get any disk
failures then it will be easy to fix.<br>
<br>
I hope the above was helpful to anyone who might try something
similar.<br>
<br>
John<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<pre class="moz-signature" cols="72">--
John Blomfield
Delivered by Thunderbird Email on Linux OpenSuse-KDE4
Old John B's Linux Notes <a class="moz-txt-link-freetext" href="http://www.oldjohnbslinux.wordpress.com">http://www.oldjohnbslinux.wordpress.com</a>
</pre>
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