vinum revive does not rebuild parity (was vinum rebuildparity,
when?)
Stijn Hoop
stijn at win.tue.nl
Tue Sep 7 21:52:29 PDT 2004
On Wed, Sep 08, 2004 at 11:28:46AM +0930, Greg 'groggy' Lehey wrote:
> >> [...] the parity surely is not correctly recalculated during
> >> the revive.
>
> If that were the case, the parity would be incorrect at offset 0.
> Yes, it is recalculated.
Of course -- I hadn't thought of that.
> >> Greg, can you tell me if this is correct behaviour?
>
> Sorry for the slow response. I was at a conference last week. No,
> it's not correct.
No problem; this is still a volunteer project last time I checked.
In a way I am glad to hear that it is not correct.
> > While not having heard back yet, I had to rebuild another subdisk,
> > but I decided to do it off-line this time. Turns out the parity was
> > rebuilt ok.
>
> Yes, this is what I recommended.
OK.
> > Might there be a bug in the online rebuild code?
>
> Looks like it.
>
> The current version of Vinum is on its last legs. Lukas Ertl is
> rewriting it, so don't expect much change in this version. For the
> time being, just accept that you should umount before rebuilding a
> plex.
I will; it's just that somehow I was led to believe that I didn't need
to do that. This has caused me some pain in the past.
May I suggest applying the attached patch to /usr/src/sbin/vinum/vinum.8?
At least it would prevent someone else from making the same mistakes as
me.
Thanks for your response,
--Stijn
--
The problem is that there are several people in design positions now who
couldn't design the Next Big Thing(TM) unless it involved them taking a
photocopier and someone else's design of The Next Big Thing(TM).
-- 'Alkaiser' in a post on Slashdot on game originality
-------------- next part --------------
--- vinum.8.orig Wed Sep 8 06:47:46 2004
+++ vinum.8 Wed Sep 8 06:51:19 2004
@@ -441,6 +441,10 @@
.Ic checkparity
prints a running progress report.
.Pp
+It is advisable to always check the parity of a RAID-4 or RAID-5 plex after
+an unclean shutdown. Corrupt parity is as bad as degraded mode for such a
+plex; if one of the subdisks of such a plex fails, data corruption will occur.
+.Pp
.It Xo
.Ic concat
.Op Fl f
@@ -1046,6 +1050,11 @@
flag is specified,
.Ic rebuildparity
prints a running progress report.
+.Pp
+At present, a bug prevents rebuildparity from correctly completing its job
+when the vinum volume is mounted and being accessed. You should only rebuild
+the parity of plexes on unmounted volumes in order to guarantee correct parity
+checks.
.Pp
.It Xo
.Ic rename
-------------- next part --------------
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