[ceph-users] what's the minimum m to keep cluster functioning when 2 OSDs are down?

Hi, With Reef, I'd like to keep the cluster functioning while 2 OSDs are down. The cluster has more than 10 nodes, each of which has 64x 2.5G threads, 256GB memory, 24x NVMe drives and 2x 25GB networking. Will k=4 and m=2 achieve what I want? I know no data loss with m=2 when 2 OSDs are down, but is the cluster still functioning/writable in that case? Or m=3 is required to keep cluster functioning while 2 OSDs are down? In case m=3, what would be the reasonable k? Overhead 1.5 or 1.6 is efficient enough for me. So, k=5 or k=6? Any comments is welcome. Thanks! Tony