Am 2011-05-04 15:23, schrieb Edward Ned Harvey:
From: linux-btrfs-owner@xxxxxxxxxxxxxxx [mailto:linux-btrfs-
owner@xxxxxxxxxxxxxxx] On Behalf Of Martin Schitter
well -- i am doing a backup of all images every night. this
process should work like a simple "scrub" because all data (and its
checksumes) will be read.
Sorry, not correct. When you read all the data using something in
user-land, the OS only needs to read one side of the data. It can
accelerate by staggering the read requests across multiple disks. So
some sectors remain unread on some disks.
When you scrub, it reads all the data from all the redundant copies
(mirrored or raid) on all the individual disks in the raid set.
ok -- i see -- you're right!
i know, there a some befits in the way btrfs and zfs implement RAID /
multiply disk usage and checksumming, but i a also want to stay on the
save side, when it comes to real practical problems. so i decided to use
'classical' linux software RAID-1 as the base layer. that's a very old
fashioned solution, but it usually simply works... and you can change a
broken disk without any respect of the used filesystem(s). in general i
try to use btrfs only on account of its snapshot features in a very
simple way.
it looks very strange to me, that i don't see any SMART warnings on the
harddisks or errors on other filsystems on the same raid-array. there
was also no reboot, power-failure or similar when the corruption
suddenly appeared. so i think, a btrfs bug would be the most evident
explanation.
martin
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