murder setup - mailboxes.db corruption - trouble recovering with ctl_mboxlist

[Andrew Morgan]

On Mon, 24 Nov 2008, Simon Matter wrote:

>> I just wanted to follow up on this thread, rather than leaving it hanging.
>>
>> It seems there was a more serious issue, which ultimately lead to the
>> failure we experienced, with our murder setup.  Specifically our
>> internal DNS servers, were having sporadic time-outs for Linux and
>> Macintosh clients.  After disabling ipv6 on both of our nameservers, it
>> seemed the name resolution issue cleared up.  The strange thing is that
>> it has been working without any complications for the last 6 months.
>> But nobody at Marshall can pinpoint anything that may have changed
>> recently with regards to ipv6 networking on the internal network.  What
>> is even stranger is that the name resolution timeouts only seemed to
>> occur on Linux and Macintosh clients, while having no harmful effects on
>> Microsoft Windows servers and clients.
>
> I had a strange issue recently with name resolution (OT because it has
> nothing todo with cyrus-imapd).
> Resolvers on Linux and recent OSX seem to always try to query for IPv6
> (AAAA) records even if NO IPv6 is configured on the client (no, I think it
> only happens if the client program tries to resolve IPv6 like firefox in
> our case). The problem starts if the DNS servers in question don't reply
> correctly to those requests and reply with SERVFAIL for example. The
> resolver will then ask the next DNS server it find in resolv.conf and go
> on until no more servers to ask, which can take quite some time if you
> have 4 servers configured like in our case.
> In the end it turned out the company in question were running DNS
> loadbalancers and they simply replied with SERVFAIL for AAAA records. I've
> been told customers with Windows don't have that problem and I guess it's
> because their resolver doesn't ask for IPv6 adresses if no IPv6 is
> configured.

I ran into an almost identical problem just yesterday with my silly home 
network router (D-Link DIR-655).  The built-in DNS server in the router 
simply ignored AAAA queries.  It didn't respond as all, even with 
SERVFAIL.  Eventually the resolver library on Linux would timeout and try 
an A query instead.  I ended up disabling the built-in DNS server and 
using the Comcast DNS servers directly.

Anyways, I can definately understand why IPv6 might cause some issues... 
:)

 	Andy