When organizations start to virtualize their physical servers, most of the time the backup of virtualized server continues to be the same: a file level based, tradional backup using an agent in the guest. Just as a physical server is treated. That’s a shame, as an image level in which the complete virtual machine file (VMDK) is being backuped is much more efficient, easier and faster to restore in case of emergency.
Several solutions are available on the market for making a virtual machine level backup, or image level backup. They all use VMware snapshot technlogy to create an instant backup of the virtual machine. Some make use of the new Changed Block Tracking feature. This new feature is part of the vStorage API. Basically the software perfoming the backup kind of asks the vSphere host ‘ hey, what blocks of data has changed since this date and time’. vSphere will respond with a list of blocks. Only these blocks are then written to backup. This saves a lot of backup time and storage on disk.
To save on diskstorage, de-dublication can be used. When a backup is made of serveral virtual machines having the operating system version in common, a lot of exactly the same files will be shared. instead of storing all of the same files multiple times, when de-duplication is used, only once instance is stored. For the other file a pointer is made to the stored file. Kind of works the same as the single instance store in use by Exchange server.
A backup is made to be used for a restore. You want your restore to be 100% guaranteed okay. This means applications running in the failed virtual machine must be restored in a consistent state without loosing data.
Mind that VMware vSphere is not able to make application consistent snapshot of Windows Server 2008 guests running a Micrsoft database application. You will need a backup tool that is able to perform the correct VSS calls. Read all about this at the Veeam blogsite
A good overview of backup strategies can be seen on the website of Chris Wolf. It is a 45 minute webinar presentation titeled “Webcast: Re-architecting Backup and Recovery for Virtual Environments
Below some links to reviews done by several people of virtual machine backup solutions:
VMware Data Recovery overview
A review of VMware disk-to-disk backup apps: Veeam, Vizioncore, PHD Virtual and VDR
Comparing the top virtual infrastructure backup tools (Veeam Backup and Replication 3.1 ,Vizioncore vRanger Pro 4 Data Protection Platform, PHD Virtual Technologies’ esXpress 3.6 VMware Backup ,VMware Data Recovery 1.0)