One of the advantages of purchasing VMware Infrastructure Enterprise (VI 3.5) is that along with the flagship ESX hypervisor there are additional licensed features and products included that are necessary to create business continuity for virtual machines (VMs). VMware Consolidated Backup (VCB) is one of these products. Often misunderstood as the complete answer for a virtual data center, VCB requires some preparation and understanding for backup administrators currently used to the traditional physical enterprise backup solution.
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VCB is not the entire backup solution for virtual infrastructure
It is very rare that VCB allows administrators to completely remove all backup agents from virtualized servers. This is because VMware Consolidated Backup does not:
- Perform specialized application backups (like Microsoft Exchange Information Store or Windows Server System State)
- Perform file-level backups of non-Windows VMs
- Provide management, cataloging or archiving of backup files
- Provide direct file restores to virtual machines
VCB is a framework of scripts that needs to be integrated with a third-party backup application to provide these features.
VCB should be installed on a dedicated Windows Server
It is recommended VCB be installed on its own server. Also known as the VCB Proxy Server, this system has the following requirements:
- Microsoft Windows Server 2003 Service Pack 1 (32‐bit or 64‐bit) or higher
- Media repository managed by the third-party backup application's management server
- The same storage protocol access as the ESX hosts to the VMFS LUNs where the VMs are stored. (i.e., host bus adapters (HBAs) for access to Fibre Channel storage or initiator configuration for iSCSI storage). Depending on the version of Windows Server used, automatic partition mounting will have to be disabled before attaching the VCB server to the VMFS LUNs
- Dedicated disk storage for the VCB Holding Tank where backup and restore files are written
- Third-party backup agent
VCB needs a large disk volume for a Holding Tank
Along with the shared access to the ESX LUNs, VCB also needs a large disk volume formatted as NTFS, which will become the Holding Tank for backup images. This volume can be on the SAN or the local VCB server's disks. The Holding Tank volume is where full VM images are placed both during backups and restores.
Therefore, the size of the Holding Tank is critical in the design. For example, if a virtual infrastructure consists of VMs that take up 1 TB of disk space and the expectation is that a full VM backup is to be taken nightly, then the Holding Tank volume needs to be large enough to support 1 TB of backups. Another scenario would be to alternate groups of full VM backups in order to decrease the required size of the volume. In this case, administrators still need to make sure the Holding Tank is large enough to hold the VM using the most disk space.
The role of the third-party backup agent
The third-party backup application does the actual backing up and management of the files. Once VCB copies a VM image to the Holding Tank it is then up to the third-party backup application to move those files to whatever media repository is in use. It is also the function of the agent to clear out the Holding Tank so that the next scheduled job has available disk space to complete.
In the case of file-level backups, VCB also mounts the copied VM image (in thumb drive style as previously mentioned) so that the backup agent can see the VM's file system. The backup agent can then perform full, incremental or differential file-level backups to the media repository. In some scenarios, the single agent on the VCB server can replace the multiple agents on the VMs.
VMware maintains a compatibility guide for supported third-party backup applications. Many of these supported applications have VCB integration modules that coordinate the scheduling of the VCB scripts and the agent backup from within the application's GUI.
Understanding VCB restore jobs
Restoring files leverages the third-party backup agent's ability to move files from the media repository back to the Holding Tank. Once the VM image is back, it can be copied in full to a VMFS volume or mounted like a thumb drive again so that individual files can be restored. An administrator must manually copy files to the restore location in both scenarios.
VMware Converter, most often used to migrate physical servers to virtual machines, can also create VMs from VCB images. Therefore, VMware Converter can be a more effective full VM restore tool in some cases. Check out VMware's Virtual Machine Backup Guide for more detailed information on implementing VCB.
About this author: Rich Brambley is a Senior Infrastructure Consultant/Engineer working for Optimus Solutions in Norcross, GA. He specializes in virtual infrastructure, and has been designing and implementing various virtualization technologies for the last five years. Prior to becoming a consultant, he held various Operations Engineer positions and was responsible for the daily administration of Wintel applications and services. He has more than 10 years experience in IT. His VM/ETC blog is dedicated to everything related to virtualization.
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