On Fri, 10 Sep 2004, Michael Loftis wrote:
Date: Fri, 10 Sep 2004 13:15:05 -0600 From: Michael Loftis <[EMAIL PROTECTED]> To: Paul Dekkers <[EMAIL PROTECTED]>, [EMAIL PROTECTED] Subject: Re: Cyrus crashed on redundant platform - need better availability?
The theory only translates if you're using a JOURNALED file system. Linux ext3, reiserfs.... AIX JFS, Sun/others veritas are all examples of this. AFAIK FreeBSD hasn't any journalling file systems, i could be wrong though since I haven't really looked for one (my freebsd boxes just run...and run...and run...) That said, the machine shouldn't' have crashed in the first place, but you are running 5.x which is clearly labeled as *NOT* production (4.10 for that)... All of my produciton boxen are 4.x based (of the FreeBSD herd)
However even a Journaled filesystem won't protect you completely from corruption. even the filesystems you list can loose data when there is a crash and if one system goes haywire and starts scribbling on the shared disk it will trash any filesystem.
David Lang
--On Friday, September 10, 2004 13:24 +0200 Paul Dekkers <[EMAIL PROTECTED]> wrote:
Hi,
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. There are two machines for redundancy. If one fails, the other one should take over: mount the disks from the array, and move on.
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, so although we have two machines for redundancy it takes still quite some time before the mail is available again. (And we still have about 90 Gb of mail to migrate, so when all users are migrated it takes much longer.) I mounted the filesystems synchronous now: although it slows down the system I hope it speeds up the fsck a bit when there is another crash. The second crash was while removing a lot of mailboxes (dm) while some of them where removed the same time using a webmail app (squirrelmail).
I'm not sure why the box crashed; there was nothing in the logs, there was nothing on the screen when we came there, it just booted up again. Of course I'm interested if anyone has any thoughts on this.
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 still takes 30 mins before everything is back again! It seems to me that if there was a "live" version of cyrus available with a synchronised mail-spool, that there was no outage noticeable for users (except in losing a connection maybe). Am I right?
Maybe it's time to continue on the "High availability ... again"-discussion we had a while ago. If the cyrus developers are able to implement this with some funding there are still some questions left for me: how much time would it take before a "stable" solution is ready? How many funding is expected? I still have to talk to management about this, but I would really support this development and I'm certainly willing to convince some managers.
Regards, Paul
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-- Undocumented Features quote of the moment... "It's not the one bullet with your name on it that you have to worry about; it's the twenty thousand-odd rounds labeled `occupant.'" --Murphy's Laws of Combat
--- Cyrus Home Page: http://asg.web.cmu.edu/cyrus Cyrus Wiki/FAQ: http://cyruswiki.andrew.cmu.edu List Archives/Info: http://asg.web.cmu.edu/cyrus/mailing-list.html
-- There are two ways of constructing a software design. One way is to make it so simple that there are obviously no deficiencies. And the other way is to make it so complicated that there are no obvious deficiencies. -- C.A.R. Hoare --- Cyrus Home Page: http://asg.web.cmu.edu/cyrus Cyrus Wiki/FAQ: http://cyruswiki.andrew.cmu.edu List Archives/Info: http://asg.web.cmu.edu/cyrus/mailing-list.html
