We have an Isilon cluster for primary storage for CIFS and NFS clients. We back it up to tape and disk libraries using 3-way ndmp. Incremental backups can be very large from time to time, so large that it seems like it might be backing up files that have not really changed. For example the current backup has transfered 1.7 million files. It seems unlikely that 1.7 million files have changed in the last 24 hours since the previous incremental (daily).
So the questions I have are -
- How are files selected for incremental backup and is there a way to modify/control it?
- Is there a way to get a report on what files were backed up in a given job and what changed in the file that caused it to be backed up?
Best answer by Harsh Desai
When running backups using NDMP, there is no Commvault software on the NAS so it relies on the OneFS file system to keep a track of the changed data. By default, the OneFS file system walks each path to identify the changes and sends Commvault the data to back it up. When you have a large number of files to back up in a data set, even if only a few files were modified, regular file system incremental backups scan all the files to check for changes, which takes a large amount of time.
This is where the fast incremental options comes in. It leverages the Dell EMC Isilon/PowerScale Changelist API for backup. Changelist tracks the changes made to files between snapshots. When you run an incremental backup, only the files that changed are scanned, so the backup is faster.
You can have Commvault send the fast incremental flag to Isilon by following the doc below:
With the above said though, in either case the files that are backed up by Commvault are selected by Isilon and not Commvault. As far as the report goes, you can run the backup job summary report and enable the option to include the protected objects to view a list of files.
Hope this helps.