Slow backup performance using NBD mode when backing up Virtual Machines.
Disable Buffer reads and writes for AVVI backups if using only NBD mode.
[HKEY_LOCAL_MACHINE\SOFTWARE\Symantec\Backup Exec For Windows\Backup
"Enable Buffered Reads"=0
"Enable Buffered Writes"=0
Note: These registry values are set to 1 by default and should be changed only if NBD mode backups alone will be used for Virtual Machines.
Symantec Corporation has acknowledged that the above-mentioned issue is present in the current version(s) of the product(s) mentioned at the end of this article. Symantec Corporation is committed to product quality and satisfied customers.
This issue is currently under investigation by Symantec Corporation. Pending the outcome of the investigation, this issue may be resolved by way of a patch or hotfix in current or future revisions of the software. However, this particular issue is not currently scheduled for any release. If you feel this issue has a direct business impact for you and your continued use of the product, please contact your Symantec Sales representative or the Symantec Sales group to discuss these concerns. For information on how to contact Symantec Sales, please see http://www.symantec.com Please be sure to refer back to this document periodically as any changes to the status of the issue will be reflected here.
Customers experiencing this issue are encouraged to contact Symantec Technical Support as data is still being collected to assist in resolving this issue.