At a Ceph Day
in Hillsboro someone, forgive me for not remembering
who, spoke of running production on servers with 2GB RAM per OSD. He
said that it was painful, required a lot of work, and would not
recommend it. ymmv.
Yeah, I wouldn't want to go below 4GB RAM.
FWIW, I have been running several production clusters with osd_memory_target = 3GB without
issues (with Nautilus / Bluestore, 4TB to 12TB hard drives and from 300 to 1400 OSDs per
cluster). I have an external caching layer for hot data though, so that cache misses on
Ceph are the common case and not an issue.
Eric