How do i start debugging ?
You would need to take a look at the logs closer to that time period in order to find out why they backup failed.
You can also use the piartool command line tool as follows, in order to gather more information about why the backup failed: "Piartool -backup -history"
This is what i see in the log:
It failed while backing few files. How could i get to know the reason why its failing for only few files ?
Sorry for crossing out few things.
This doesn't really provide us more information than your original screenshot. Could you take a look at the message logs in SMT > Operations > Messages and set the start and end times around the time the backup was taken. In here there should be additional information on why the backup is failing beyond the -16915 error we're seeing.
From PI message logs
May be the disk wasn't available to PI Backup when "Virtual Disk Service" started. What do you think ?
The "returned invalid File Handle" indicates to me that perhaps the PIBackup subsystem doesn't have access to the directory where those files are and the fact that it's intermittent makes me wonder if this is a virus scan or the like that's temporarily locked the files and preventing you from backing them up if it takes too long.
@Robert Schmitz' advice is spot on. The log files might reveal something else or could reveal issues stemming from any one of the following suggested checklist items that might be helpful when PI Backups fail:
Some of those come from my own experience.
Thanks James !
Retrieving data ...