seen db

[Bron Gondwana]

On Wed, Jun 11, 2008 at 10:52:31AM +0200, Rudy Gevaert wrote:
> Bron Gondwana wrote:
>> There you go.  We've had the 64bit kernel approximately forever, but only
>> just upgraded from 2.6.20 series to 2.6.25.
>>
>>> I can try with a 32bit kernel tomorrow.
>
> Unfortunate with the 32bit kernel 2.6.24-2 it sync_server still segfaults.

Try a 2.6.20 kernel, just for an interesting datapoint.  We changed
back to 2.6.20 (64 bit still) and haven't seen a corrupted seen file
since.

>> Oh - can you tell me.  Did the file checkpoint sometime not too long before it
>> got corrupted?
>
> The cases I saw it did.

Ditto here.  Interesting.  They also had quite long records, but
I don't know how common that is.  Lots of little bits of seen
spread around the space.

>> I've got a small set of theories, but I'm reading the skiplist source code
>> (again!) to see if they make sense...
>>
>> Bron.
>
> I'm also wondering if what would happen if I brought up a master. Surely 
> the imap processes would also segfault.  Right?

If it was on those corrupted files, yes.  On that machine - quite
probably.  If you can afford the hardware it may be worth testing.

(hmm, I can possibly dedicate a 64 bit capable machine to testing
this.  If it's a kernel bug I'd love to reproduce it)

> Here I can delete the mailbox on the replica and sync again.  As a  
> reconstruct doesn't help.

We find reconstructing helps now - but that's with the 2.6.20
kernel.  There were multiple things going wrong before.  We
originally suspected the external drive unit was playing up,
but I'm thinking kernel now.

Bron.