After upgrading to NetBackup 7.5.0.x, VMware Backups are slower than expected

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  • Article ID:000016741


The performance of VMware Backups may be slower than expected after an upgrade to NetBackup 7.5.0.x due to a performance issue surrounding host disk caching which is taking place within the API of the VDDK (Virtual Disk Development Kit).


The issue was caused by a newly added setting in a VDDK library to enable caching by default:

vixDiskLib.disklib.EnableCache = 1

This setting was expected to increase the speed of VMware Backups - however, the opposite has been seen.


Upgrade to NetBackup or NetBackup Appliance version 2.5.1.

If an upgrade is not possible, please edit the following files.

Make a backup copy of vixDiskLib.ini.  This configuration file can be found in the following path:

C:\Program Files\Common Files\VERITAS\VxMS\shared\VDDK\vixDiskLib.ini

Appliance VMware Backup Host:

There is an Emergency Engineering Binary (EEB) available for the 2.5 ( appliance that will address the issue. Please contact Symantec support and request the EEB associated with ET3044870.

Linux VMware Backup Host:
# /usr/openv/lib/shared/vddk/vixDiskLib.ini

Edit vixDiskLib.ini by changing the following entry:

vixDiskLib.disklib.EnableCache = 1


vixDiskLib.disklib.EnableCache = 0


On a Linux system, the folder does not exist by default:

# echo "vixDiskLib.disklib.EnableCache = 0" > /usr/openv/lib/shared/vddk/vixDiskLib.ini

Information on this setting was taken available from the VDDK Documentation at this link:

vixDiskLib.disklib.EnableCache – Caching by vixDiskLib is off by default. This variable turns caching on. The disadvantage of caching is that although you get some performance improvement, you risk getting stale data if programs go directly to the disk. Acceptable values are 0 for Off and 1 for On.

This document may be updated in the future if this issue is resolved in a future version of NetBackup.  Please use the Subscribe via email link above to receive notification of such updates.


Applies To

This issue has been found in:
NetBackup 7.5 to
NetBackup Appliance version 2.5

Terms of use for this information are found in Legal Notices.



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