I just read an interesting article today by Bridget Bothello pointing out that automated virtualization disaster recovery is not a silver bullet.
While the article used VMware's Site Recovery Manager (SRM) as an example, it alludes to limitations of all VM-based HA and DR: While these tools provide simplified failover, remember that they only apply to vendor-specific virtualized instances. The article referenced Mike Laverick, a VMware and Citrix Certified Instructor who wrote a book on SRM.
Here's the gotcha: Nearly all environments have both physical and virtual applications - and short of creating independently-managed DR and HA "silos", there aren't too many ways to unify P & V DR/HA. Said Laverick of this quandry (and I quote) "It is such a royal PITA."
There are a few products on the market that can unify DR replication of HW environments from bare metal, regardless of whether they consist of physical instances or virtual hosts. For example, Egenera's PAN Manager software will replicate an entire HW, network & storage environment (and provision new VM hosts) in a matter of minutes.
But this all begs a few Q's:
- Do we really expect production to virtualize 100% of applications?
- What apps are unlikely to be virtualized? And,
- How desirable is mixed P & V HA/DR?
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Good discussion points.
I am always amazed at the number of organisations who have little idea how (and potentially more importantly when) they should provide DR capability.
When looking for energy efficiency improvements having servers idle is one of the first areas to address.
Does it really matter in most cases if recovery takes an extra couple of minutes ?
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