Re: read-from-all-disks support for RAID1?

[Kalin KOZHUHAROV <kalin@thinrope.net>]

Lennert Buytenhek wrote:
> (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 ;-)

Well, an option might be good for debugging, but it will lower performance
a lot, IMHO.

As log as 3-drive RAID1 is concerned :-) You'd better get RAID3 or 2
more drives and RAID5.

Kalin.

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