I was recently investigating a situation where certain NetBackup 6.5.4 backups that utilized VCB 1.5 U1 were taking an unusually long time to complete. For example, a 350 GB backup of a virtual machine was taking almost 8 hours! This was a LAN-free backup of a virtual machine sitting on a Clariion SAN. Something was definitely wrong.
It didn't take too long to find Document ID 323230, where Symantec reports a bug described as slow VCB backups and explained that "This occurs when the NTFS File system is handling large files." There was also a fix introduced in NetBackup 6.5.5 that allows the ability to export virtual machine disk (vmdk) files as 2GB chucks instead of a single monolithic file. This sounded like a promising fix.
Now facing a change request for a NetBackup upgrade, I went to look at the release notes for the latest version of VCB - 1.5 U2. Under the resolved issues section of the release notes, it states that "Performing backup of virtual machines containing .vmdk files greater than 50GB with the vcbmounter -M1 (monolithic export) command takes longer duration compared to vcbmounter -M0 command. The issue is fixed in this release." NetBackup was definitely using the monolithic export, so I decided to simplify things a bit and just upgrade VCB to the latest version first. I perceived the VCB update as a quicker win with less risk.
Upgrading VCB to the latest version was simple. I stopped the NetBackup services, installed VCB 1.5 U2, verified the VCB install was a success (as detailed in the release notes), and finally restarted NetBackup services. Running the same backup job for the 350 GB virtual machine now completes in less than 3 hours. The next step will be to upgrade to NetBackup 7, where these times should improve even more!
As always, thanks for reading!