VM Data Protection Primer: Comparing Data Protection Strategies for Virtual Server Environments - Page 2

Jay Kramer (Profile)
Monday, January 18th 2010

Tradeoffs: While client-based backup is simple to implement and has the broadest application support, it requires you to carefully manage backup application schedules to minimize I/O impact. It may also require addition backup application licenses.

Console Backup

In this model, the administrators use an application to protect the virtualized environment that is independent of the backup application, such as PureDisk or Avamar. These applications deduplicate the VM data and only send the unique new data to their master server. This model typically requires a separate management server and storage that is independent of the traditional backup environment.

Tradeoffs: Depending on the licensing model, this approach could save some licensing costs and it will minimize LAN bandwidth. It also provides capacity reduction through deduplication. However, you cannot use standard enterprise backup software with these solutions. As a result, application consistency may be difficult to maintain. It also creates a challenge around disaster recovery since console backup applications will typically need to replicate their deduplication repository for disaster recovery purposes.

VMware Consolidated Backup (VCB)

With the VCB model, you use VMware’s snapshot functionality to take an image of a running VM and the image is then presented either as a share or an entirely separate windows proxy server.  The proxy server is then backed up using a traditional backup application such as NetBackup or TSM.

Tradeoffs: This model is endorsed by VMware and it minimizes backup impact on physical servers. However, it can add considerable complexity in managing the snapshot and mounting processes. The challenge of managing the proxy host and VCB mounting process can be difficult. In addition, the snapshot functionality primarily supports Windows and can be difficult to implement in other environments. Note that the number of VMs per server is limited to 20 due to I/O constraints.

Storage Level Backup

Storage level backup uses storage arrays to snapshot existing volumes. Snapshots provide the benefit of instant creation and recoverability, but in order to maintain snap consistency VMware integration is required. It enables you to retain multiple snapshots online.

Tradeoffs: This is only supported by a limited number of array vendors and it can be costly to purchase snapshot capacity and licenses. You must be able to replicate snapshots for disaster recovery and retention may be limited by the number of snapshots supported by the array.

VMware vSphere

vSphere is a new VMware backup application with a complete list of changed data allowing you to peform a true incremental backup. It provides the fastest incremental VM backups and a simper recovery process.

Tradeoffs: Currently only supported by a limited number of backup applications.


There is no single approach to protecting virtual environments that is right for everyone.  Each approach has benefits and challenges and it is up to IT to decide the best option for their environment.  The first approach is the simplest and most straight forward and in practice, the vast majority of virtual server users are relying on this approach.  Most end users start with the first model and look to other options when they encounter problems or are planning on adding new hardware/software solutions to their environment.