Standby Continuous Replication (SCR) and “High-Availability”

 07 Dec 2007 06:01:36 pm

I’ve seen quite a few articles lately talking about SCR and referring to it (or putting it in the same bucket as) High-Availability solutions. Even Microsoft has done this with some of their documentation (i.e. Yes if you delve deeper into the documentation you’ll see that they refer to SCR as a ‘resilience’ feature (which is much more accurate) however I don’t think a lot of their customers are receiving or understanding this message.

Because of this I’ve actually run into several customers who were “waiting for SP1 to be released” because they wanted to build “highly available solutions” (obviously this was prior to its release last week).

SP1 does introduce one multi-site high-availability “feature”, and that is support for Server 2008 (due to be released Q1 '08 ). Server 2008 adds in MSCS support for multi-site clustering so you could extend your CCR Cluster across the WAN*, but this is really a Server 2008 feature and not so much an Exchange 2007 SP1 feature. If this is what those customers are after they need to be waiting for Server 2008!

That said why do I say it’s not a “High-Availability” feature, a couple of very important reasons:
• It requires manual ‘failover’ to your standby server
• Legacy Outlook clients (i.e. Outlook 2003) will not automatically reconnect to the standby server, they would need to have their profile updated

So, if you want High Availability continue use of your CCR and SCC clusters for mailboxes. If you want Disaster Recover/Resiliency look into SCR.

-Erik Szewczyk

*There are some caveats here with a CCR or SCC cluster in Exchange 2007, for example they must be part of the same AD Site.

Category : Exchange | Posted By : Erik | Comments [0] | Trackbacks [0]


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