I am looking for a viable way to get incremental "backups" from GPFS snapshots without using TSM (or a comparable software)? The background is that, in a planned system, updated files should just be copied somewhere else (outside GPFS) periodically and that has to be controlled somehow.
I am thinking of that approach: One could do snapshots at regular points in time, say T_1, T_2, .... Then, in order to run a backup at time T_i, one would inspect which files have actually data blocks in the snapshot from T_(i-1) (meaning they have been changed since T_(i-1) ), and read those from snapshot T_i. That might be quicker than an inode scan if the change rate is low and there are many inodes, I think. Is there an easy way to identify those files which do have data in the snapshot (which is a prereq. for that approach to work at all)?
As an alternative, the use of the api for inode scans (like in ts_inode) should be considered I suppose. A question WRT this: objects in a snapshot have the same inode (number) as their sources - how would the indode scan distinguish that (or does it just ignore all snapshot objects)?