In a 3 node cluster with EC k=2 m=1, you can turn off one of the nodes and the cluster will still operate normally. If you lose a disk during this state or another server goes offline, then you lose access to your data. But assuming that you bring up the third node and let it finish backfilling/recovering before restarting any other nodes, then you're fine.
On Thu, Oct 19, 2017 at 4:49 PM Jorge Pinilla López <jorp...@unizar.es> wrote: > Imagine we have a 3 OSDs cluster and I make an erasure pool with k=2 m=1. > > If I have an OSD fail, we can rebuild the data but (I think) the hole > cluster won't be able to perform IOS. > > Wouldn't be possible to make the cluster work in a degraded mode? > I think it would be a good idea to make the cluster work on degraded mode > and promise to re balance/re build whenever a third OSD comes alive. > On reads, it could serve the data using the live data chunks and > rebuilding (if necessary) the missing ones(using cpu to calculate the data > before serving// with 0 RTA) or trying to rebuild the missing parts so it > actually has the 2 data chunks on the 2 live OSDs (with some RTA and space > usage) or even doing both things at the same time (with high network and > cpu and storage cost). > On writes, it could write the 2 data parts into the live OSDs and whenever > the third OSD comes up, the cluster could re balance rebuilding the parity > chunk and re positioning the parts so all OSDs have the same amount of > data/work. > > would this be possible? > > ------------------------------ > *Jorge Pinilla López* > jorp...@unizar.es > Estudiante de ingenieria informática > Becario del area de sistemas (SICUZ) > Universidad de Zaragoza > PGP-KeyID: A34331932EBC715A > <http://pgp.rediris.es:11371/pks/lookup?op=get&search=0xA34331932EBC715A> > ------------------------------ > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >
_______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
