Cyrus crashed on redundant platform - need better availability?

[Sebastian Hagedorn]

Hi,

--On Freitag, 10. September 2004 13:24 Uhr +0200 Paul Dekkers 
<Paul.Dekkers at surfnet.nl> wrote:

> We're implementing a new mailplatform running on two dell 2650-servers (2
> xeon cpu's with each 3 Ghz, HTT and 3Gb of memory) and with a disk array
> of 4 Tb connected with a adaptec 39160 scsi controller for storage. We
> installed FreeBSD 5.2.1 on it, and - of course - cyrus 2.2.8 (from the
> ports) as IMAP server. Our MTA is postfix.

that's similar to our setup, be we are currently running Red Hat Advanced 
Server 2.1, Cyrus 2.1.16 and sendmail.

> There are two machines for redundancy. If one fails, the other one should
> take over: mount the disks from the array, and move on.

Right, works fine for us for the most part. Hasn't always been like that, 
but the most recent kernel updates by Red Hat have improved matters a lot.

> Unfortunally, the primary server crashed twice already. The first time it
> did while synchronising two IMAP-spools from the old server to the new
> one. There was not much data on it back then. The second time was worse,
> around 10Gb of mail was stored on the disks. We discovered that the fsck
> took about 30 minutes,

Isn't your filesystem journaled? We use ext3 for ours. There *have* been a 
few occasions where the journal had been damaged as well (forcing us to run 
fsck), but those have been few and far between. In all other instances the 
failover is nearly instantaneous.

> Although many on the list claim that this (having 2 boxes with 1
> disk-array) is a nice way for redundancy I'm in doubt now if this is
> true.

It's good but not perfect. We recently installed a huge SAN and are now in 
the process of moving over the mail data to reside there. Fibrechannel 
seems to be much more error tolerant than SCSI.

Cheers, Sebastian Hagedorn
--
Sebastian Hagedorn M.A. - RZKR-R1 (Gebäude 52), Zimmer 18
Zentrum für angewandte Informatik - Universitätsweiter Service RRZK
Universität zu Köln / Cologne University - Tel. +49-221-478-5587
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