On Tue, Dec 5, 2023 at 5:16 AM Patrick Begou <Patrick.Begou@xxxxxxxxxxxxxxxxxxxxxx> wrote: > > On my side, I'm working on building my first (small) Ceph cluster using > E.C. and I was thinking about 5 nodes and k=4 m=2. With a failure domain > on host and several osd by nodes, in my mind this setup may run degraded > with 3 nodes using 2 distincts osd by node and the ultimate possibility > to loose an additional node without loosing data. Of course with > sufficient free storage available. > When the failure domain is the host, then k/m are referring to hosts, so to have k=4,m=2 you'd need an absolute minimum of 6 hosts, but that would be pushing it. To start to actually use all that space they'd need to be equally balanced, and that configuration wouldn't allow for any kind of recovery if you lost a host, until you add a new one. You typically want more hosts than k+m. With only 3 hosts size=3, min=2 is probably the best way to go, as inefficient as it is. Keep in mind that distributed filesystems in general, and especially ceph, tend to work best when you have a very large number of hosts. If you want host-level redundancy and EC you need a fair number of them. I'm just running a home cluster so I get by with less than 10, but I would not seriously consider my current config for any kind of serious use, and I'm not using k=4,m=2. Rich _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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