On Fri, Sep 12, 2014 at 01:57:37AM -0700, shane-ker...@csy.ca wrote: > Hi,
> I am testing BTRFS in a simple RAID1 environment. Default mount > options and data and metadata are mirrored between sda2 and sdb2. I > have a few questions and a potential bug report. I don't normally > have console access to the server so when the server boots with 1 of > 2 disks, the mount will fail without -o degraded. Can I use -o > degraded by default to force mounting with any number of disks? This > is the default behaviour for linux-raid so I was rather surprised > when the server didn't boot after a simulated disk failure. The problem with that is that at the moment, you don't get any notification that anything's wrong when the system boots. As a result, using -odegraded as a default option is not generally recommended. > So I pulled sdb to simulate a disk failure. The kernel oops'd but > did continue running. I then rebooted encountering the above mount > problem. I re-inserted the disk and rebooted again and BTRFS mounted > successfully. However, I am now getting warnings like: BTRFS: read > error corrected: ino 1615 off 86016 (dev /dev/sda2 sector > 4580382824) > > I take it there were writes to SDA and sdb is out of sync. Btrfs is > correcting sdb as it goes but I won't have redundancy until sdb > resyncs completely. Is there a way to tell btrfs that I just > re-added a failed disk and to go through and resync the array as > mdraid would do? I know I can do a btrfs fi resync manually but can > that be automated if the array goes out of sync for whatever reason > (power failure)... I've done this before, by accident (pulled the wrong drive, reinserted it). You can fix it by running a scrub on the device (btrfs scrub start /dev/ice, I think). > Finally for those using this sort of setup in production, is running > btrfs on top of mdraid the way to go at this point? Using btrfs native RAID means that you get independent checksums on the two copies, so that where the data differs between the copies, the correct data can be identified. Hugo. -- === 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 --- SCSI is usually fixed by remembering that it needs three --- terminations: One at each end of the chain. And the goat.
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