Disaster Recovery Using VMWare ESX

Posted on 2009-05-26
Medium Priority
Last Modified: 2012-05-07
Hi all,

I'm currently implementing a DR solution using VMWare ESX.

We have 15 VM's which run on our 2-host ESX cluster.  Four of these are 'critical' - Exchange 2007, a DC, web server and file server, and I am going to replicate these to our DR site just across the road.  The DR site has an ESX host attached to it's own iSCSI SAN (same setup as primary site).

I'm using esXpress from PHD to back up the critical VM's (both system and data disks/vmdks) to an NFS target.  It's installed on both production ESX hosts and on the 3rd 'DR' esx host.

The backups run 3 times a day.  As the backups are block-level rather than incremental or full, they complete pretty quickly.  The 3rd ESX host is set to restore those backups from the NFS target on a schedule, so at the DR site I have a working copy of my four critical VM's.

My question is less VMWare-related and more AD/Exchange related.  In the event of one or more critical VM's going down, the plan is to simply log onto the 3rd ESX host and connect the replicated VM's virtual network adapter to the network.  As the replicated machines have the same IP's, names etc (they are an exact copy), I'm pretty sure this should work, certainly in the case of the file server.  My question is, am I likely to run into issues bringing up DC's and Exchange servers that are snapshots from a few hours previously?.  From an AD point of view, we have a second physical DC, so DC that I bring up at the DR site should be bought up to date via AD replication - it's just Exchange 2007 I'm not sure about now.

For example, one thing I'm unsure about is that the clock on the replicated VM will be a few hours behind the actual time when I first bring it up - ie at 15.00 the main Exchange server goes down, I bring up the replicated Exchange VM, which is from the backup that ran at 0900, therefore the system clock initially will be somewhere around 09:00.  Once it synchs with the domain the clock should roll forward, but is that likely to cause issues with logging etc?

Can anyone see any other potential flaws in this plan..?  Obviously I'm going to test it all, but it would be nice to be aware of any potemtial pitfalls at the outset.

Thanks for your time.



Question by:markholmes24
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Expert Comment

by:Manpreet SIngh Khatra
ID: 24472248
The data on the Exchange would be some time back in case of DB info, but recomendation would be Outlook users in Cache mode so data loss can be prevented. Exchange does not replicate any info between each other so less chances of a problem.
Utmost what we might have to do in a scenario, where the Exchange has died but DC's are alive is to run the /recoverserver switch.

Author Comment

ID: 24472446

Many thanks for your comments.

Our clients are running in Cached mode, yes.

I really should have mentioned in my original post, that we are using Backup Exec Continuous Protection with GRT to protect the Exchange stores, so no email should be lost.  So the process for bringing up Exchange at the DR site would go:-

1) Connect replicated VM to virtual network and power on
2) Run restore to bring all DB's up to date



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Expert Comment

by:Manpreet SIngh Khatra
ID: 24472729
Cool thats the way to go ......
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Expert Comment

by:Manpreet SIngh Khatra
ID: 24490660
Mark did you try implementing or just the information that was required ?
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Accepted Solution

Manpreet SIngh Khatra earned 1500 total points
ID: 24490672
One more recommendation that i would give is that if you have a DR please have a planning at a different Geographical location.

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