Just watch how many snapshots you create. We hit an issues around 4,700 snapshots of a singe file system. See: https://www.spinics.net/lists/ceph-devel/msg38203.html Eric On Fri, Sep 15, 2017 at 12:25 PM, Sage Weil <sage@xxxxxxxxxxxx> wrote: > 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 -- 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
