CephFS: How to create with different size?

[gkovacs]

When creating a regular (RBD) Ceph pool, there are options in both the GUI and in pveceph to determine the size (replication count) and the min. size (online replicas for read) of the pool. However, when creating a CephFS pool, neither the GUI, not pveceph provides an option to create one with a different size, and the default values of size=3 and min.size=2 are used.

I would very much like to configure a CephFS pool with a size=2 and min.size=1, how is that possible?

 

[t.lamprecht]

We omitted that when initially introducing this as we tried to start small and assumed that >90% can work with the safe defaults of 3/2, as using higher object counts is not often seen in practice and using 2/1 is unsave, so we wanted to avoid that users not famillar with ceph, and/or the implications of 2/1 can select it.

If you know what you do and can live with split brains and data loss you could create MDS over WebUI/API and the pools and cephfs itself manually through ceph tool.
Just pass "-c /etc/pve/ceph.conf" as option directly after "ceph" and you should be good.