Is BTRFS safe on top of an md array?
Been suffering from bitrot every now and then and I'm considering on changing from ext4 to btrfs.
BTRFS on md raid
-
-
Bitrot?? How do you know?
You should be able to use btrfs on top of mdadm. You could use zfs all by itself too.
-
Well, main use of this box is to host my music library, which is exactlly as downloaded from DC++
which has SFV checking built in, and that's how I find the rot.
Once in a while I remove and re-add the shared folders to initiate a rehash.
Then all the corrupt files pop out cause they fail sfv check.I need the flexibility of md for shrinking and expanding my raid.
If zfs could do that I would be there already but...So you recon I could convert my ext4 md raid6 to btrfs without data loss?
-
Do you have this happen often? I can't believe you would have more than one file fail and this wouldn't be very often. The sfv checking looks like a crc32 check. If something altered the tag in the file, it would change the checksum. I don't think you would every have audible bitrot in music or audible/visible in movies.
Do you shrink and expand your array often? I know you can expand zfs (maybe not from the plugin).
You can convert ext4 to btrfs. Would I do it without a backup? Nope.
-
The library is read-only from the media player side. Only DC++ can change files.
So it's not from changed tags and so. I have this library about 8 years now and I've
grown it a couple of times plus moved it to a new omv install/hardware a couple of times...ZFS only supports expanding by adding stripes... Which is not what I want.
I need the one drive add/remove ability of md...Hm... So I guess I should stay put until btrfs is stable...
-
Btrffs on top of mdadm will not give you bit rot recovery. As far as I know data profile still doesn't allow DUP, but is in plan. @igrnt can probably confirm this or not.
You can safely use the multi device btrfs with raid1 or raid10 (kernel 3.16 at least). Raid56.....if you have backups do it. But you need to be on at least kernel 4.3. Raid56 data scrubbing is one of the features in testing currently -
ok, thanx for the heads-up!!
-
You could use unionfilesystem plugin with snapraid. SnapRAID would give you the bitrot protection. Your music collection probably doesn't need realtime parity. I know this doesn't help with your current filesystem but I think it is a good option.
-
DUP for data - on a single device only - was recently added (4.4? Not sure if it needs the up-to-date kernel or just tools), so you could do this on top of an md RAID array. However, it is not absolutely guaranteed to protect you from checksum errors in the same way as multi-device redundancy in btrfs, since some devices, SSDs especially, may not actually write two true copies to the disk.
As others have said, to protect against bitrot btrfs really needs to handle the RAID itself.
Jetzt mitmachen!
Sie haben noch kein Benutzerkonto auf unserer Seite? Registrieren Sie sich kostenlos und nehmen Sie an unserer Community teil!