Hi, Sage I find that several issues related to current CRUSH algorithm as below: 1. It is possible to select out the same collision and retry bucket in a crush_choose_firstn() loop. (e.g. when we set reweight to 0 or mark osd out, it would be definitely rejected if it is selected. However, when the second chance to select out another one based on the different r', it is still possible to select out the same osd previously rejected, right? And until a different one is selected after several retries.). I think we can record those rejected or collision osds in the same loop so that the process can be converged much faster? 2. Currently, the reweight params in crushmap is memoryless (e.g we balance our data by reducing reweight, which will be lost after this osd DOWN and OUT automatically. And we mark its IN again because currently ceph osd in directly marks the reweight to 1.0 and out marks the reweight to 0.0). It is quite awkward when we use ceph osd reweight-by-utilization to make data balance (If some osds down and out, our previous effort is totally lost). So I think marking osd "in" does not simply modify reweight to "1.0". Actually, we can iteration the previous osdmap and find out the value of the reweight or records it anywhere we can retrieve this value again? 3. Currently, there is no debug option in the mapping progress in Mapper.c. dprintk is default disabled so that it will be hard to dig into the algorithm if something unexpected result happens. I think we can introduce the debug options and output the debug information when we use "ceph osd map xxx xxx" so that it is much more easier to find the shortness in current mapping process? Regards Ning Yao -- 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
