Accelerator notes and requirements for virtual machines
Note the following about Accelerator for virtual machines:
Accelerator for virtual machines uses VMware Changed Block Tracking (CBT) to identify the changes that were made within a virtual machine.
VMware CBT may occasionally reset tracking of file changes, such as after a power failure or hard shutdown. In that case, for the next backup NetBackup reads all the data from the vmdk files and the backup takes longer than expected. If deduplication is enabled, the deduplication rate is lower than expected.
For more information on CBT, see the following VMware article:
Supports the disk storage units that have the following storage destinations:
Cloud storage. Storage that a supported cloud storage vendor provides.
NetBackup Media Server Deduplication Pool. In addition to NetBackup media servers, NetBackup 5200 series appliances support Media Server Deduplication Pool storage.
Qualified third-party OpenStorage devices.
To verify that your storage unit supports Accelerator, refer to the NetBackup hardware compatibility list for the currently supported OST vendors:
See the NetBackup compatibility lists.
It is recommended that you do not enable Expire after copy retention for any storage units that are used with storage lifecycle policies (SLP) in combination with Accelerator. The Expire after copy retention can cause images to expire while the backup runs. To synthesize a new full backup, the SLP backup needs the previous backup image. If the previous image expires during the backup, the backup fails.
Update the NetBackup device mapping files if needed.
The NetBackup device mapping files contain all storage device types that NetBackup can use. To add support for the new devices or upgraded devices that support Accelerator, download the current device mapping files from the Cohesity Technical Support website.
See the NetBackup Administrator's Guide Volume I for information on the device mapping files and how to download them.
Storage unit groups are supported only if the storage unit selection in the group is Failover.
Supports the full backups and incremental backups. Every Accelerator backup (from a full schedule or incremental schedule) results in a complete image of the virtual machine.
You can use incremental backups (cumulative or differential) as follows: To reduce the file-mapping overhead and to reduce the number of files that are recorded in the NetBackup catalog. Cumulative backups may involve more file-mapping because they do not use the random indexing method to determine which files have changed. In some cases, differential backups may be faster than cumulative backups.
If a backup of the virtual machine does not exist, NetBackup performs a full backup. On the backup host it also accesses the VMware CBT information. This initial backup occurs at the speed of a normal (non-accelerated) full backup. Subsequent Accelerator backups of the virtual machine use VMware Changed Block Tracking to accelerate the backup.
Note:
When you first enable a VMware policy to use Accelerator, the next backup (whether full or incremental) is in effect a full backup: It backs up all the virtual machine files that are selected in the policy. If that backup is an incremental, it may not complete within the backup window.
If the storage unit that is associated with the policy cannot be validated when you create the policy, note: The storage unit is validated later when the backup job begins. If Accelerator does not support the storage unit, the backup fails. In the bpbrm log, a message appears that is similar to one of the following:
Storage server %s, type %s, doesn't support image include.
Storage server type %s, doesn't support accelerator backup.
Accelerator requires the storage to have the
OptimizedImageattribute enabled.Because of a VMware restriction, BLIB is not supported for VMware templates. As a result, NetBackup Accelerator cannot be used to back up VMware virtual machine templates.