2010
11.04

With some incredulity, I just read a story on TechCentral.ie  where Veeam says that:

“44% of IT directors say they avoid using virtualisation for mission-critical workloads because of concerns about backup and recovery. At the same time, only 68% of virtual servers are, on average, backed up, according to the study of 500 IT directors across Europe and the US”.

That’s pretty damned amazing.  Why do I say that?  Because I know one MS partner here in Ireland sells Hyper-V because it makes backups easier and more reliable.

Hyper-V features a volume shadow snapshot service (VSS) provider.  This allows compatible backup solutions (there’s plenty out there) to safely backup VM’s at the host level.  This means that backing up a VM, its system state, its applications, and its data is a simple backup of a few files (it’s a bit more complicated than that under the hood).  From the admins perspective, it’s just like backing up a few Word documents on a file server. 

Here’s the cool bit.  When a Hyper-V VM is quiesced, the VSS providers within the VM also start up.  Any file services, Exchange services, SQL, and so on, are all put into a safe state to allow a backup to take place with no service interruption.  Everything is backed up in a safe, consistent, and reliable manner.  The result is that the organisation has a backup of the entire VM that can be restored very quickly.

Now compare being able to backup a VM by restoring a few files comapred to doing a complete restoration of a physical server when some 2-5 year old piece of tin dies.  You won’t get identical hardware and will have lots of fun restoring it.

BTW, if a physical piece of tin suddenly dies in a Hyper-V cluster then the VM just fails over to another host and starts working there.  There’s no comparison in the physical world.  Sure you can cluster there but it’ll cost you a whole lot more than a virtualisation cluster and be a lot more complicated.

Sounds good?  It gets better.  Backing up a Hyper-V cluster at the host level is actually not a good idea (sounds odd that something good starts with something bad, eh?).  This is because a CSV will go into redirected more during the backup to allow the CSV owner complete access to the file system.  You get a drop in performance as host I/O is redirected over the CSV network via the CSV owner to the SAN storage.  We can eliminate all of that and simplify backup by using VSS enabled storage.  That means choosing storage with VSS providers.  Now you backup LUNs on the SAN instead of disks on a host.  The result is quicker and more reliable backups, with less configuration.  Who wouldn’t like that?

2 comments so far

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  1. Just reading your article, and at the end you mention, “We can eliminate all of that and simplify backup by using VSS enabled storage”. Can you give a real example of how this would work with some product? Is this this just snapshots built into the storage unit, which can be considered backups?
    We’ve just set up a Hyper-V Server 2008 R2 cluster with a Dell MD3220i and BackupExec 2010 R2 for backups. We’ll be doing VM backups from the CSV which will use the Redirected Access state, but if there’s a better way, I’d love to know about it.

    • The recommended solution is to buy storage that has a hardware VSS provider that _supports_ CSV. Your backup solution will then
      Need to know how to use the provider. In a HP P4000, this initiates a SAN snapshot to quickly do the snap. It’s quicker, more scalable, and minimises redirected i/o.

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