On 2018年03月23日 19:04, james harvey wrote: > If a system unexpectedly reboots during a balance, what's the best next step?
Normally, nothing. Btrfs CoW is pretty safe for most case. > > From an ISO, read-only operations/mounting looks fine. > > Didn't want to make any writes until I ask, because I see some reports > of bad things happening with a reboot during a balance, and don't want > to mis-step. At least, with my test using balance and dm-log-writes (a tool can not only emulate powerloss, but also be able to do a write-by-write analyse), it shows some false alerts about btrfs check, but the result looks pretty safe so far. (Even for the false alert case, btrfs check --mode=lowmem works just fine) > > btrfs check reports no errors. mount -o ro,skip_balance works fine > and directory entries seem correct. Then nothing to worry about. If you want more safety, run "btrfs check --check-data-csum" to double check your data before RW mount. Thanks, Qu > > $ sudo btrfs balance status -v /mnt/tmp > Balance on '/mnt/tmp' is paused > 0 out of about 0 chunks balanced (0 considered), -nan% left > Dumping filters: flags 0x17, state 0x0, force is off > DATA (flags 0x0): balancing > METADATA (flags 0x0): balancing > SYSTEM (flags 0x0): balancing > > This surprised me. Not sure if it's expected for an interrupted or > paused balance to show 0/0/0/nan. > > Do I re-mount without "ro,skip_balance" and see if it finishes the > balance? (If it doesn't, cancel and restart it?) > > Do I re-mount without "ro" but still with "skip_balance", and cancel > the balance and restart it? (Never trying to continue the interrupted > balance?) > > Something else that I'm not aware of? > > ... System didn't reboot on its own, it became completely unresponsive > for over 24 hours, and I had to perform a hard reset. Active ssh > sessions permanently hung, and local logins didn't get past asking for > password. Hoped I could get a btrfs balance cancel to run. > > > > $ uname -a > Linux terra 4.15.8-1-ARCH #1 SMP PREEMPT Sat Mar 10 00:00:33 UTC 2018 > x86_64 GNU/Linux > > $ btrfs --version > btrfs-progs v4.15.1 > > $ sudo btrfs fi show /mnt/tmp > Label: 'losable' uuid: 9208dacc-8bb3-4303-9f71-124f0cecc7e7 > Total devices 4 FS bytes used 6.92TiB > devid 1 size 2.50TiB used 1.78TiB path /dev/mapper/lvm-losable1 > devid 2 size 2.50TiB used 1.78TiB path /dev/mapper/lvm-losable2 > devid 3 size 2.50TiB used 1.78TiB path /dev/mapper/lvm-losable3 > devid 4 size 2.50TiB used 1.60TiB path /dev/mapper/lvm-losable4 > > $ sudo btrfs fi df /mnt/tmp > Data, RAID0: total=6.92TiB, used=6.91TiB > System, RAID1: total=8.00MiB, used=400.00KiB > Metadata, RAID1: total=7.00GiB, used=5.77GiB > GlobalReserve, single: total=368.09MiB, used=0.00B > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >
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