On Fri, Jul 06, 2012 at 02:51:43AM -0600, Alexander Block wrote: > On Fri, Jul 6, 2012 at 12:34 AM, Goffredo Baroncelli <kreij...@libero.it> > wrote: > > On 07/05/2012 06:51 PM, Alexander Block wrote: > >> Hello all, > >> > >> in IRC we had a discussion on how we could solve sending live > >> subvolumes and how to send subvolumes without the need to > >> administrate/keep old snapshots for incremental sends. One of the > >> ideas was to introduce "sendshots", which are basically snapshots > >> where no refs are counted for file data. This means, that when file > >> data is changed in the sendshot origin, we do not consume extra space > >> for two copies of the data. We would only have the metadata > >> duplicated. > >> > >> For the initial btrfs send we could do this: > >> 1. Create a hidden read-only snapshot of the subvolume to send. Hidden > >> means that it's not referenced by any subvolume. It is however still a > >> normal snapshot (not a sendshot!). Hidden snapshots are not possible > >> atm so we would have to implement that. This step allows us to send > >> read-write subvolumes, because we have a freezed version of it. > > > > Why we should want/need an hidden snapshot ? We could put this kind of > > hidden snapshot under a directory dot-prefixed (like /.hidden-subvolumes) > That would have the problem that the user may modify the subvolume > in-between (by removing the ro flag). Or he could simple cd into it > and we would later fail to delete it.
I prefer to make this more explicit. We could add a hard-readonly flag that cannot be cleared. Having the snapshot show in the FS lets the admin know what things are really using space. -chris -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
