On 2017年12月17日 03:50, Dark Penguin wrote: > Could someone please point me towards some read about how btrfs handles > multiple devices? Namely, kicking faulty devices and re-adding them. > > I've been using btrfs on single devices for a while, but now I want to > start using it in raid1 mode. I booted into an Ubuntu 17.10 LiveCD and > tried to see how does it handle various situations. > The experience left > me very surprised; I've tried a number of things, all of which produced > unexpected results. > > I create a btrfs raid1 filesystem on two hard drives and mount it.
Initial info like "btrfs fi df" will help us to dig this further. > > - When I pull one of the drives out (simulating a simple cable failure, > which happens pretty often to me), the filesystem sometimes goes > read-only. ??? Please provide the kernel message. > - But only after a while, and not always. ??? > - When I fix the cable problem (plug the device back), it's immediately > "re-added" back. But I see no replication of the data I've written onto > a degraded filesystem... Nothing shows any problems, so "my filesystem > must be ok". ??? Needs extra info like "btrfs fi df" > - If I unmount the filesystem and then mount it back, I see all my > recent changes lost (everything I wrote during the "degraded" period). > - If I continue working with a degraded raid1 filesystem (even without > damaging it further by re-adding the faulty device), after a while it > won't mount at all, even with "-o degraded". Please provide kernel message too. Although I doubt about the usefulness, it's still better than none. Thanks, Qu > > I can't wrap my head about all this. Either the kicked device should not > be re-added, or it should be re-added "properly", or it should at least > show some errors and not pretend nothing happened, right?.. > > I must be missing something. Is there an explanation somewhere about > what's really going on during those situations? Also, do I understand > correctly that upon detecting a faulty device (a write error), nothing > is done about it except logging an error into the 'btrfs device stats' > report? No device kicking, no notification?.. And what about degraded > filesystems - is it absolutely forbidden to work with them without > converting them to a "single" filesystem first?.. > > On Ubuntu 17.10, there's Linux 4.13.0-16 and btrfs-progs 4.12-1 . > >
signature.asc
Description: OpenPGP digital signature
