In a prior post, we explored an article by Paul Venezia over at InfoWorld who has a great article entitled When Virtualization Becomes Your Worst Enemy.  His overall thesis can be summarized as virtualization can go from being your best friend to your worst enemy when problem start occurring within your IT infrastructure.  The reason is that the physical server consolidation (more virtual machines running on fewer physical machines) means that if a single physical server fails, you have a much wider impact.  When virtualization becomes your enemy, technology, such as backup, becomes your best friend.

So as I note at the close of the prior post – if virtualization can become your enemy in this situation, and backup is your friend, how do you make sure that you can rely on your friend?  The key attributes you’re looking for in your ”friend” (i.e., backup) here are flexibility and heterogenity.

What do I mean by flexibility and heterogeneity?  What always concerns me in backup is how flexible a solution is.  For example, I’ve heard passionate arguments about whether HOS (Host Operating System) or GOS (Guest Operating System) backup is superior.  Of course, if you’re a virtual-only product you’re going to argue HOS is superior because that’s all you support; if you’re AppAssure or any other Windows-only vendor you’re going to argue that GOS is better because that’s all you’ve got.  If all you have is a hammer, the whole world looks like a nail.

The truth is that the best solution often depends on the specifics of the customer’s environment.  Typically HOS-level backup works wonderfully; however, GOS-level backup lets you protect VM-attached NASs, physical RDMs, granular inclusion/exclusion of data, granular replication, protection of free (unlicensed) VMware ESXi (VMware purposely doesn’t allow HOS-level protection of free ESXi), and the like.  There can be performance differences between the two as well – however, beware of sweeping performance or overhead claims by vendors that don’t support both.

Another major reason I like flexibility and heterogeneity is that I’ve run into situations where there are defects in HOS-level API sets that can be solved with GOS-level APIs, or vice versa.  This is relatively rare – but I’ve found that when it comes to data protection, paranoia is a healthy attitude.

How about you?  Have any thoughts on HOS- versus GOS-level backup or flexiblity and heterogenity in general?