Ceph

http://ceph.com/docs/master/install/hardware-recommendations/

Specifically a user was asking for a better description of hardware requirements for OSDs. Several users chimed in with good advice of "it depends on OSD size" and a good 'rule of thumb' that has been trending on the mailing list has been 1GB/1TB of RAM/disk. I think there are a few places in the docs where we mention this and it would be good to be a) consistent and b) a bit more directed in our guidance of scale, rather than use explicit values.