read-from-all-disks support for RAID1?

[Lennert Buytenhek]

(please CC on replies)

Hi!

I recently had a case where one disk in a two-disk RAID1 array went
subtly bad, effectively refusing to write to certain sectors without
reporting an error.  Basically, parts of the disk went undetectably
read-only, causing file system corruption that wouldn't go away after
fsck, and all kinds of other fun.

Would it be hard/wise to add an option for RAID1 mode to read from all
devices on a read, and report an error to syslog or simply return an
I/O error if there is a mismatch?  (Or use majority voting and tell
people to use 3-disk RAID1 arrays from now on ;-)


thanks,
Lennert
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