It depends on how long ago (in terms of data writes) it disappeared. Each PG has a log of the changes that have been made (by default I think it's 3000? Maybe just 1k), and if an OSD goes away and comes back while the logs still overlap it will just sync up the changed objects. Otherwise it has to do a full backfill across the PG. -Greg Software Engineer #42 @ http://inktank.com | http://ceph.com On Fri, Feb 21, 2014 at 10:33 AM, Tim Bishop <tim-lists@xxxxxxxxxxx> wrote: > I'm wondering how Ceph deals with OSDs that have been away for a while. > Do they need to be completely rebuilt, or does it know which objects are > good and which need to go? > > I know Ceph handles well the situation of an OSD going away, and > rebalances etc to maintain the required redundancy levels. But I'm > unsure what it does when an OSD comes back some time later still > containing data. > > Tim. > > -- > Tim Bishop > http://www.bishnet.net/tim/ > PGP Key: 0x6C226B37FDF38D55 > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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