On Sun, May 11, 2014 at 05:53:40PM +1000, brett.k...@commandict.com.au wrote: > Hi,
> I created a RAID10 array of 4x 4TB disks and later added another 4x > 3TB disks, expecting the result to be the same level of fault > tolerance however with simply more capacity. Recently I noticed the > output of 'btrfs fi df' lists the Data layout as 'single' and not > RAID10 per my initial mkfs.btrfs -d raid10 -m raid10 /dev/... > command. That's odd. Was it fully RAID-10 before you added the other devices? Looking at the btrfs fi df output, there's no vestigial "single" chunks for your metadata, so it's been balanced at least once. What can happen is that if the FS is balanced when new (i.e. with no data in the data chunk -- so "touch foo" isn't sufficient), the data chunk(s) are removed because there's no data in them. With no data chunks at all, the FS then can't guess what type it should be using, and falls back to single. > Is this single data layout due to the overall inconsistent disk size > used ? e.g. it can no longer fully stripe across all disks hence > simply concatenates the subsequent smaller disks and displays this > as an overall 'single' Data layout. No, it should be fine. With a balanced RAID-10 in your case, it will fill up all 8 devices equally, until the smaller ones are full, and then drop from 8 devices per stripe to 4, and continue to fill up the remaining devices. > I require fault tolerance hence ultimately want to know if I > actually do have a RAID10 data layout, else should try perhaps a > 'btrfs fi balance start -dconvert=raid10 /export' (assuming enough > free space exists). Yes, that would be the thing to do. Note that you'll be _very_ close to full (of not actually full) after doing that, based on the figures you've quoted below. You have 4*3.64 + 4*2.73 = 25.48 TiB of raw space, which works out as 12.74 TiB of usable space under RAID-10, so you're within 100 GiB of full. I'd suggest, if you can, shifting 100 GiB or so of data off to somewhere else temporarily while the balance runs, just in case. > I also noticed there are 2x System layouts shown, which leads me to > think perhaps the first disks (4x4TB) are laid out as RAID10 for > Data however the subsequent disks (4x3TB) are simply concatenated, > giving me hopefully a limited level of fault tolerance for now. You'll note that the System/single is empty -- this is left over from the mkfs process. There would originally have been similar small empty chunks for Data and Metadata, but these will have gone away on the first balance. As it stands, though, your data is not fault tolerant at all -- but you're in with a good chance of recovering quite a lot of it if one disk fails. Hugo. > [root@array ~]# uname -a > Linux array.commandict.com.au 3.14.2-200.fc20.x86_64 #1 SMP Mon Apr 28 > 14:40:57 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux > [root@array ~]# btrfs --version > Btrfs v3.12 > [root@array ~]# btrfs fi show > Label: export uuid: 22c7663a-93ca-40a6-9491-26abaa62b924 > Total devices 8 FS bytes used 12.66TiB > devid 1 size 3.64TiB used 2.12TiB path /dev/sda > devid 2 size 3.64TiB used 2.12TiB path /dev/sde > devid 3 size 3.64TiB used 2.12TiB path /dev/sdi > devid 4 size 3.64TiB used 2.12TiB path /dev/sdg > devid 5 size 2.73TiB used 1.21TiB path /dev/sdb > devid 6 size 2.73TiB used 1.21TiB path /dev/sdf > devid 7 size 2.73TiB used 1.21TiB path /dev/sdh > devid 8 size 2.73TiB used 1.21TiB path /dev/sdj > > Btrfs v3.12 > [root@array ~]# btrfs fi df /export > Data, single: total=13.25TiB, used=12.65TiB > System, RAID10: total=64.00MiB, used=1.41MiB > System, single: total=4.00MiB, used=0.00 > Metadata, RAID10: total=19.00GiB, used=16.47GiB > [root@array ~]# > > Thanks in advance, > Brett. -- === Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk === PGP key: 65E74AC0 from wwwkeys.eu.pgp.net or http://www.carfax.org.uk --- The glass is neither half-full nor half-empty; it is twice as --- large as it needs to be.
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