RE: Exchange Server Redundancy

  • From: "Mulnick, Al" <Al.Mulnick@xxxxxxxxxx>
  • To: "'[ExchangeList]'" <exchangelist@xxxxxxxxxxxxx>
  • Date: Tue, 2 Mar 2004 10:54:03 -0500

I'll offer both for what it's worth.
Clustering is not a redundancy solution.  It's a high availability solution
(HA). Redundancy infers no downtime while HA infers that you can withstand a
hardware failure and can be up and running much more quickly than you could
with manual intervention.  
For 30 users you want to weigh the costs.  You can achive this, but wouldn't
it be cheaper and almost as fast to have the parts on hand and just replace
them if they go bad?  Hardware is fairly reliable these days and that can be
more cost effective and easier to work with.  Clusters are only a little
more difficult than a standalone (IMHO) but they do have additional
licensing costs for many third party applications that you use to support
your infrastructure.  AV, Backup, etc fit this category typically.
As for active/active clusters with other apps on them. You can do this.  It
is possible, but again the complexity goes up with each application as does
the requirement to monitor more closely and provision more appropriately in
case of failover (think about it, if you fail over a node due to hardware
failure, you have to have the resources to absorb the added burden.  This
often indicates bigger hardware components to handle the load.) Multiple
apps on an Exchange server are not always straightforward and easy as
Exchange likes to live alone as do other apps.  I'll reiterate that it can
be done, but is it worth it in your environment?
check out
<>  for some helpful docs.


From: Jason Merrique [mailto:j.merrique@xxxxxxxxxxxxxxx] 
Sent: Monday, March 01, 2004 7:15 PM
To: [ExchangeList]
Subject: [exchangelist] Exchange Server Redundancy

Hi All,
One of our exchange servers experienced a hardware failure this morning
(excellent start to the week!), and as it was the main mailbox store, it
caused a few hours of downtime for most of our users. To prevent this from
happening again, I'd like to have a certain amount of redundancy. I
understand that in a cluster of exchange servers this is possible as they
effectively act as one logical exchange server. 
Is it possible to achieve the same level of redundancy without setting up a
cluster, by synchronising the mailboxes between the two servers?
Would a cluster be overkill for our two servers and 30 odd users?
As part of an exchange cluster - would it be possible for the server to take
on other tasks as an individual?
If you could offer personal advice, or a recommendation of literature, that
would be excellent.
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