On 20/02/2013 09:01, Reindl Harald wrote:
Am 20.02.2013 00:52, schrieb Gordan Bobic:
On 02/19/2013 10:00 PM, Reindl Harald wrote:
data without a raid are useless
My point was that even RAID is next to useless because it doesn't protect you against bit-rot.
it does
OK, say you have RAID1. One of the disks has a rotted sector. Your RAID
implementation can detect that the mirrors don't match but there's no
way to tell which is correct without an additional checksum.
Similar for RAID5 - you can detect that the data doesn't match the
checksum, but you have no way of being able to tell which n out of n+1
blocks are correct.
and in case of
RAID you have to have at least one full backup
and so it does not care me if disks are dying
Depends how many versioned backups you have, I suppose. It is possible to not notice RAID silenced bit-rot for a
long time, especially with a lot of data
what do you think why a weakly raid-check is running
per default and any high-grade RAID does srub?
My point is that there isn't enough data in n+1 (RAID[1|5]) to work out
which set of blocks is correct to rebuild the data from. With RAID6 you
can do this, but not with lower levels of RAID.
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