Re: btrfs and ECC RAM

George Mitchell
2014-01-20T16:07:51Z

After reading the recent posts on this topic I am beginning to think
there is some real confusion between "check sums" and "parity". These
are two different things which serve two different purposes. In each
case, bad RAM would have different repercussions. But I still fail to
see how, in the case of either btrfs or zfs, bad RAM could damage data
via the checksum process. In fact, I would expect that checksum would
guard against that very thing. If not, checksum is very badly
implemented. Most of the world uses non-ECC RAM. I simply cannot
believe that a file system like zfs would expose the user to more risk
than ext4. I think there is some very inappropriate panic going on over
this thing. Just because one source has asserted that something like
this can happen does not make it fact. As it concerns zfs, it needs to
be brought up at a zfs forum, not here. As it concerns btrfs, I think
it has been made clear by some of the sharpest contributors here that
this is not going to pose any risk with btrfs. If a btrfs checksum
fails, btrfs is not going to change anything if it cannot find a copy
that passes checksum, and bad RAM is not going to cause bad data to pass
checksum. But I CAN see how bad RAM could affect parity calculations
and resulting data IN THE ABSENCE of protective checksums and cannot
help but wonder if THAT is what the original article is describing.