Thursday, August 25, 2011

Getting Started With Virtualization Aware Backups

The first thing to understand is where are you in your virtualization journey? Sometimes in virtualization we forget that there are still many companies that have not yet even started their virtualization project and there are many, many others that have started it but are now looking for ways to enhance it. The first challenge that both of these types of organizations run into is how to back up their newly virtualized environment.

Most organizations will start with using a legacy backup application and install the backup agent inside each virtual machine. This quickly becomes a challenge as potentially dozens of backup jobs get kicked off at the same time on the same hosts. The overall host performance is impacted as is the performance of each individual VM.

The first thing new virtualization projects and projects that are now trying to grow beyond the initial wave of virtualization need to look for is a backup application that does not require that the backup software be installed in each individual VM. This is now done by communicating with the VMware vStorage API that allows for external processes like backup to communicate directly with each virtual host and not have to impact each virtual machine.

Advanced Virtualization Backups

With the basics out of the way, the next step is to look for applications and processes that truly leverage the virtual environment. Again this is done through features provided by VMware and by features within the application. One of the more critical of which is changed block tracking (CBT). This capability allows the backup application to only have to backup the blocks that have changed of the virtual machine image since the last backup. The result is very fast backups and very low impact to VMs while the backup is occurring. This means backups can now be done more than once per day, reducing the amount of data that is lost when an application or server fails.

While there are a few vendors that support CBT for backups Avamar is the first we’ve seen which does that and something called change block recovery. This can be a critical feature and compares well against other backup applications that are doing in-place recoveries.

With recovery in place solutions you have to run the VM from the backup device, which in almost all cases is not as fast as production storage. You can use VMware’s Storage Vmotion to migrate the data live back to the production storage system. That migration has to happen typically over an IP segment so the migration could take a while on larger virtual machines. Comparatively, CBT recovery allows you to restore only the blocks that have changed between the current version of the data and the point that you want to roll back to.

The net impact is that while you may be effectively down with changed block recovery, it is typically going to be for just the few minutes it takes to restore just those changed blocks of data back to a production storage system. At that point you are running at full storage performance, not crippled by the speed of the backup device that was not designed to run production applications and is also replicating the instance back to a production storage system. Avamar of course has deduplication, which eliminates redundancy between virtual machines, between physical hosts and even stand alone servers that are not yet virtualized. Avamar protects both virtual and non-virtual servers.

Backup is a key ingredient to a successful server virtualization roll out and it is a key enabler of a more full virtualization ROI. For just a little bit at VMworld, take a break from the clouds and see if you can improve your backup strategy.

George Crump, Senior Analyst