I guess whats really hard to program: snapshot removal when not copying the data, but only pointing to that data and writing the differences from that point on. Figure out how difficult it is to remove snapshot 3 of 7; When snapshot 1 is the original data, snap2 the diff from 1 to 2, snap 3 the diff from 2 to 3, .... so you have to merge the data of snap 3 and 4. But the benefits are obvious: instant snapshots and very low space consumption (in case you don't delete lots of your 'live' data). On 8/5/09, Andrey Kuzmin <andrey.v.kuzmin@xxxxxxxxx> wrote: > On Wed, Aug 5, 2009 at 3:18 PM, Roy Sigurd Karlsbakk <roy@xxxxxxxxxxxxx> > wrote: >> >> On 4. aug.. 2009, at 20.33, Chris Mason wrote: >> >>>> It's strange that such a small thing should be delayed so much. If >>>> snapshot removal was working, I'm quite sure we might get more users >>>> and thereby more stable code faster. >>> >>> It's a small feature but it gets deep into the difficult parts of the >>> dentry cache to do it right. So, it definitely isn't easy. >> >> >> I'd say it's a pretty elemetary feature to be able to remove something you >> have created. > > Snapshots are somewhat counter-intuitive in many respects: for > instance, one snapshot-capable file-system performs writes to a > dataset with snapshots _faster_ than to the same dataset w/o > snapshots. Snapshot removal is no exception - it's a bit more complex > than one would think. > > Regards, > Andrey > >> I know, you can remove the files and so on, but still, having a bunch of >> old and empty >> snapshots lying around is no good. > > >> >> roy >> -- >> Roy Sigurd Karlsbakk >> (+47) 97542685 >> roy@xxxxxxxxxxxxx >> http://blogg.karlsbakk.net/ >> -- >> I all pedagogikk er det essensielt at pensum presenteres intelligibelt. >> Det er et elementært imperativ for alle pedagoger å unngå eksessiv >> anvendelse av idiomer med fremmed opprinnelse. I de fleste tilfeller >> eksisterer adekvate og relevante synonymer på norsk. >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
