C Anthony Risinger wrote: > On Nov 29, 2010, at 3:48 PM, Andrey Kuzmin <andrey.v.kuz...@gmail.com> > wrote: > >> I'm not sure why zfs came up, they don't own the term :). As to >> zfs/overhead topic, I doubt there's any difference between clone and >> writable shapshot (there should be none, of course, it's just two >> different names for the same concept). >> >> Regards, >> Andrey >> >> >> >> >> On Tue, Nov 30, 2010 at 12:43 AM, Mike Fedyk <mfe...@mikefedyk.com> >> wrote: >>> On Mon, Nov 29, 2010 at 1:31 PM, Andrey Kuzmin >>> <andrey.v.kuz...@gmail.com> wrote: >>>> This may sound excessive as any new concept introduction that late >>>> in >>>> development, but readonly/writable snapshots could be further >>>> differentiated by naming the latter clones. This way end-user would >>>> naturally perceive snapsot as read-only PIT fs image, while clone >>>> would naturally refer to (writable) head fork. >>>> >>> I'm not sure we want to take all of the terminology that zfs uses as >>> it may also bring the percieved drawbacks as well. Isn't there some >>> additional overhead for a zfs clone compared to a snapshot? I'm not >>> very familiar with zfs so that's why I ask. >>> >> -- >> 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 > > I don't like the idea of readonly by default, or further changes to > terminology, for several reasons: >
I quite agree with you. LVM2 also defaults to read/write for snapshots. > ) readonly by default offers no real enhancement whatsoever other than > breaking _anything_ that's written right now This was the first thing that came to my mind. > ) btrfs readonly is not even really readonly; as superuser could > simply flip a flag to enable writes, readonly merely prevents > accidental writes or misbehaving apps... ie. protecting you from > yourself > ) backups are the simple/obvious use case; I personally use btrfs > heavily for LXC containers, in which case nearly every single snapshot > is intended to be writable -- usually cloning a template into a new > domain > ) I also use an initramfs hook to provide system rollbacks, also > writable; the hook also provides multiple versions of the "branch"... > all writable > ) adding new terms is not a good idea imo; I've already spewed out > many sentences explaining the difference between subvolumes and > snapshots, ie. that there is none... adding another term only adds to > this problem; they each describe the same thing, but differentiate > based on origin or current state, neither of which actually describe > what it _is_-- a new named pointer to a tree, like a git branch -- a > subvolume. > > I think a better solution/compromise would be to leave snapshots > writeable by default, since that's more true to what's happening > internally anyway, but maybe introduce a mount option controlling the > default action for that mount point. > > C Anthony [mobile] -- 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
