[CentOS] clustered mail server?

Sun May 18 10:41:56 UTC 2008
Johnny Hughes <johnny at centos.org>

Rudi Ahlers wrote:
> Karanbir Singh wrote:
>> Rudi Ahlers wrote:
>>> Well, that's one of the problems I foresee, but also the fact that 
>>> each email has a unique message ID, so I don't know if the backup 
>>> server will pickup the changed messages ID's or not? I have been 
>>> thinking of running a MySQL backed mail server, but have a feeling it 
>>> will have a heavy impact on performance

DRBD is a block device ... there is no difference in a database or 
files.  I database in the shared partition is JUST a file anyway :D

>> umm. message-ID's are added at mail origin time ( or the first time 
>> they come in contact with a non brain dead mta ).
>> me thinks you need to read up a bit on what email is and how it works. 
>> the RFC's are a good place to start ( and mostly readable ).
> I'm referring to the way qmail stores emails (if each email is a 
> different file). AFAIK, this is a known problem with clustered mails 
> servers.

DRBD is not really clustered in that since, at least not the normal setup.

DRBD is BASICALLY raid1 for specific hard drive partition.  It does not 
copy files, it copies underlying bits directly as a block device.

I use DRBD effectively on Domain Controllers / File Servers and on 
e-mail servers.  I have MySQL databases and LDAP databases and 
Qmailtoaster in the box on these with no problems whatsoever.

There is a way to setup a Primary-Primary type on a clustered file 
system like GFS or OCFS2, however that is not the main purpose of DRBD. 
  The main purpose is to replicate a partition and fail it over to 
another machine when the first one fails.

Both partitions in a DRBD group are not mounted at the same time (much 
like RAID1) and you only access what is know as the secondary device 
when it becomes primary, unless you use the Primary-Primary setup.  But 
there are much better ways (IMHO) to achieve Primary-Primary effect with 
other clustering technologies like LVS or RHCS/RHGFS.

Johnny Hughes

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 252 bytes
Desc: OpenPGP digital signature
URL: <http://lists.centos.org/pipermail/centos/attachments/20080518/ede350f0/attachment-0005.sig>