The time and computation costs are minimal. The main problem you will run into is that taking a snapshot forcefully pushes out a transaction group. Normally, ZFS tries to sync transaction groups every 3-5 seconds in order to group enough data together but not waiting too long to commit (non-ODSYNC) data to disk. Depending on your circumstances, forcing these transaction groups out at a higher frequency may impact performance. There is an open RFE to have "deferred snapshots" that don't force a sync, but it's unlikely to get attention any time soon given other priorities.
- Eric On Fri, Mar 21, 2008 at 09:55:38AM -0700, Tim Wood wrote: > Hi, > I'm interested in the overhead of making, cloning, and destroying > snapshots. It sounds like the cost for all of these is low, but how > low?? > > For example, could I make snapshots of a system every 5 seconds? > every second? More often than that? > > I'm primarily interested in the time/computation cost of doing these > operations, but also about the storage cost. > > Would it be plausible to do something like take snapshots twice a > second on a disk with a low/moderate load? If I only cared about the > last 60 seconds worth of snapshots, would that make things much slower > since I'd constantly be eliminating old checkpoints? > > Also, I [i]think[/i] that a while back I saw a technical paper on > ZFS's design, but I have not been able to track it down again. Does > anyone know if this exists? -- Eric Schrock, Fishworks http://blogs.sun.com/eschrock _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
