Recently I encountered an outage where on a SQL Server cluster where a disk resource was taken offline. Netbackup had initiated a backup of the file system right at the time of the outage. It turned out that the Volume Shadow Copy storage location was changed, thereby creating a depenceny between disks and the Cluster took the disks offline "by design" to update the dependencies. I've been unable to determine what triggered the change in the volume shadow copy settings. VSS or windows will not do that on it's own of course, and no user interaction occurred. Veritas tells me that Netbackup only inherits the VSS settings from windows.
I have read http://technet.microsoft.com/en-us/library/cc779378(WS.10).aspx where MS says in essence: dont change or enable shadow copeis on deployed clusters because doing so will take your disks offline... but that doesnt help me to understand what inititate the change to begin with.
Has anyone seen behavior like this, whereby some backup software creates a volume shadow copy from disk X on disk Y thereby creating a new dependency and taking a resource offline?