Backup and Xen


Great discussion over at Spiceworks concerning Xen – not XenServer, but Xen. I’m going to also cover here since there are some important issues being discussed here if you use Xen.

The thread over at Spiceworks is here.

Of course, the difference between Xen and XenServer is that one is open sourced and a community effort (Xen) and the other is a product from Citrix (XenServer.) Open source version of Xen as you rightly call out are often deployed in cloud environments. Also, open source Xen setups are quite often managed by virtualization experts who not only have a good knowledge on Xen but also are required to build a support structure of tools and utilities (typically scripts) to automate tasks like backup leveraging tools such as rsync and tools like “xm save” and “xm restore.”

Okay – first, and I realize it goes without saying, you can backup treating the guest VM was if it were physical. The advantage of course is highly flexible and granular backup of each VM. But this isn’t host-level backup.

For host-level backup, because Xen always uses Linux as its privileged domain, and because Unitrends supports a flexible file-based Linux backup paradigm, you can use pre- and post-commands to save and restore the VMs at the host level. You can then back that up as a standard file and clean it up with a post command.

Also, for host-level backup, since open source Xen setups do not have a built in snapshotting mechanism for data protection, many administrators have setup their servers such that LVM or SAN snapshots can be leveraged for data protection. The scripts used to protect open source Xen can be integrated with Unitrends appliances natively via pre and post commands.

Okay – on to your question – which I interpret as “when will Unitrends support Xen (as opposed to XenServer) at a host level on a highly granular basis?” The answer is – we’re waiting right now on a more mature set of data protection APIs to develop in Xen that we can take advantage of in creating a host-level agent. We did VMware first – it was clearly the most mature with VADP and CBT. We’re releasing Hyper-V this month – less mature whch meant a whole lot more work by our developers in terms of implementing features such as CBT. Next we have XenServer in our sights – with their recent work on a snapshot API and XenServer’s third-place market share that’s the reason for the prioritization.

Once the backup and snapshotting framework for Xen is put in place by the Xen community, and as the market share of Xen continues to grow, it will get put onto our roadmap. But for now, I don’t know precisely when we’ll support it beyond the capabilities I mention above.

Does that make sense – or am I missing something?


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