[i]I think you're just looking for frequent backups, not necessarily capturing every unique file version.[/i]
Thanks for your reply, Joe, but this is not my intention. I agree, that my arguments here look like moving targets. They simply developed along the lines of discussion. I'd still target every unique file version. Of course, not the transient ones, only those versions that have been written completely to disk. We will for a looong time not be able to reconstitute each and any moment in time. Though I am pretty sure, we can achieve a reconstitution of each and any moment of a completed write operation. If Nico was correct, the whole of ZFS wouldn't make sense. If Nico was correct, even with 'the other operating system' data would frequently be lost. Just think of a crash, a power outage without UPS: We don't know the states of the files, but in 99.9% of the cases, the states of the files on the hard drive allow for a proper reboot. Meaning, AFAICS, that the state of files on a hard drive is usually consistent. Even with VFAT, or UFS. When I do very frequent backups (once per minute, e.g.), I get a lot of overhead, metadata, system activity; on almost all unmodified files. And still, I might miss out a relevant change. I was arguing in the other post that once I do very very frequent backups (once per second, e.g.) I will be fine, because I have the state before and after that second. Even *true* CDP would probably not require that intermediate state (again, aside from some specific applications, like databases; but that is solved within the applications), which also might not have been completely written to the drive. This is - I understand - where Nico is in agreement with me. Any completed write needs to be CDP-ed. And here we reach square one: while all those inotify-s and file_events_notification are needed for TimeMachine, my fear is still that they work on too high a level, need too many resources. As I wrote I have no clue about the internals of ZFS, but was hoping the file system itself could do all the necessary. > If configured to approach CDP behavior on rapidly changing filesystem, one > can imagine > ADM hammering a filesystem and still not keeping up. Again, too frequent polling is wasting resources. As long as we have the notion of time-induced backups, we're lost in any case. But even polling a flag and getting into action is wastage. Again, probably the file system itself needs to know how and perform the right action on its own. Uwe This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
