VMware ESX "Continuous Availability" Feature to Enable Crash Consistent Transactional Database Replication?
Help me understand if I'm reading this right.
The problem with replicating VM's at the server level (rather than with a client inside the virtual machine a la DoubleTake) using today's technology is with any transactional databases on those VM's. Machines that are relatively static work very well with system-level VM replication tools like esxReplicator and Double Take for Virtual Systems. But, any time you add in an Exchange, SQL, or Active Directory database (to name but a few), the replicated VM at the DR site won't necessarily come back on-line in a crash consistent state once you flip to your DR site.
Mike Laverick writes in his blog last week about some of the new technologies coming out of VMworld. Among the many is one that catches my eye called "Continuous Available for ESX".
According to Mike...
Last he ends with a “High Availability” section. Detailing the “record the execution” feature now available experimentally in Workstation 6 where real-time activity is recorded and logged to disk, and replayed at will for application debugging purposes. This new feature has been dubbed “Continious Available” for ESX. In this case you have a primary and second VM on two different ESX hosts. The primary VM on the primary ESX host is continuelly sending the record data to the other VM - not to a log file. The two VMs held in synch. In the demo, when Mendal clicked the start menu you saw this happen on two VMs on two different ESX hosts at the SAME time! See it like two VMs mirrored. Next the pulled power cords out the back of the primary ESX host - and the other VM just kept on running. It was an Exchange server with 100+ of emulated user activity… So this is great - what everyone has been asking HA to do, which currently does do. Sounds great huh? But just remember if the primary VM has a BSOD - so will its mirror…
I wasn't able to make it to VMworld this year (sad, but true). So, I'm reading about it from afar as people write up their reports. Am I reading it right that this new feature, to be released with a future version of ESX will enable database replication from the system level?
If true, than this has every likely to be the killer app for the next version of ESX. I say "killer" because there are a few companies out there doing VM replication. If we start getting replication that works right within our VM licenses, that elevates ESX's value far beyond anything -- and likely puts some level of concern into 3rd party vendors who do this...
Mike's write-up can be found here:
http://www.rtfm-ed.co.uk/?p=434
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Comments
Did you try using Neverfail for Exchange. That's a very good software and it worked in every single case for me.
Posted by: Dimitry | October 8, 2007 7:53 AM