Usually, for any non-Windows VMs, anything that is not/cannot be covered by SYMCquiesce - Including Red Hat and SUSE VMs that have unsupported file systems - the NetBackup Client should be installed for agent based backups. (So, no VMware VADP type backups.)
Unless, you can time a cron job script to flush and freeze your unsupported file system before each backup job starts, and long enough for the backup to complete. The timing and scheduling could be a bit tricky.
Perhaps it may be possible to utilize the parent_start_notify script on the Master server so that when a VMware VADP job starts, the Master would run your custom script which could call another script on the client for the ReiserFS flushing and freezing. After the backup has completed, a parent_end_notify could be used the same way for thawing.
I would recommend just installing the client for Standard type backups for the whole client, or, VMware VADP type backup for the whole VM plus a another Standard type policy (agent/client based) just for the ReiserFS mount point.
