On Sun, 26 Dec 1999, Jakob Østergaard wrote:
> Am I correct in assuming that it is _ONLY_ under reconstruction that swapping
> on RAID is not safe ?
>
> I've been rather busy lately (still am) so I didn't read the bug report... Is this
> reconstruction/swap bug present in all RAID levels (with redundancy of course) or
> is it limited to RAID-5, -1, or -4 ?
Any RAID level that may resync (1, 4, 5, etc) is unsafe for swap (or for
journaling filesystems for that matter). And yes, it is only at
resync time that it is dangerous (AFAIK).
It has something to do with raid resync using the buffer cache and swap (and
filesystem journaling) not... it's a fundamental problem with the left hand
not knowing what the right hand is doing.
> Originally the HOWTO had a nice explanation as to why it was NOT safe to
> swap on RAID, but then the bugs were corrected (the known ones at that time
> at least) and the statement was corrected accordingly. I'll correct it once
> again, as soon as I know exactly what to write :)
Thanks - that's a good idea. It's not a happy surprise... :-)
Stephen Tweedie ([EMAIL PROTECTED]) explains the problem in:
http://www.progressive-comp.com/Lists/?l=linux-raid&m=94449239719591&w=2
-Andy
