I know people have been disscussing on and off about providing a "preferred OSD" for things like multi-datacenter, or even within a datacenter, choosing an OSD that would avoid traversing uplinks. Has there been any discussion on how to do this? I seem to remember people saying things like 'the crush map doesn't work that way at the moment'. Presumably, when a client needs to access an object, it looks up where the object should be stored via the crush map, which returns all OSDs that could be read from. I was thinking this morning that you could potentially leave the crush map out of it, by setting a location for each OSD in the ceph.conf, and an /etc/ceph/location file for the client. Then use the absolute value of the difference to determine preferred OSD. So, if OSD0 was location=1, and OSD1 was location=3, and client 1 was location=2, then it would do the normal thing, but if client 1 was location=1.3, then it would prefer OSD0 for reads. Perhaps that's overly simplistic and wouldn't scale to meet everyone's requirements, but you could do multiple locations and sprinkle clients in between them all in various ways. Or perhaps the location is a matrix, so you could literally map it out on a grid with a set of coordinates. What ideas are being discussed around how to implement this? -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
