On Fri, 15 Sep 2017, Two Spirit wrote: > Excellent. Yes was takling about CephFS. So basically it tags and > versions all objects and their corresponding metadata. Doesn't > actually replicate anything, and keeps the old objects around in the > OSDs? Something like that. :) s > > On Fri, Sep 15, 2017 at 10:37 AM, Sage Weil <sage@xxxxxxxxxxxx> wrote: > > On Fri, 15 Sep 2017, Two Spirit wrote: > >> few questions > > > > I'm assuming you're talking about CephFS snapshots here: > > > >> 1) Is the idea of snapshotting about 100TB of data doable with Ceph? > > > > You can snapshot the entire file system (petabytes) if you like. > > > >> 2) How long would such a task take? Are we talking seconds, minutes, > >> hours, days, weeks? > > > > Seconds (if that). > > > >> 3) what does "stop i/o" mean. Does the filesystem unavailable to the > >> user during the snapshot time, or is this administratively unavailable > >> to the user, or does ceph stop io somewhere while in parallel the data > >> can be read/written to? > > > > There's no IO stoppage. Clients essentially mark a barrier in their > > writeback caches so that previously buffered writes are contained in the > > snapshot and new writes are not. How long it takes for that data to be > > flushed and stable/durable on OSDs depends on how big your client caches > > are, but that does not cause any io stoppage or gap in availability for > > users of the file system. > > > > sage > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" 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 ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
