Hello, Reading http://ceph.com/docs/master/ops/manage/grow/placement-groups/ and thinking to build a ceph cluster with potentially 1000 OSDs. Using the recommandations on the previously cited link, it would require pg_num being set between 10,000 & 30,000. Okay with that. Let's use the recommended value of 16,384 ; this is alreay about 160 placement groups per OSD. What if, for a start, we choose to reach this number of 1000 OSDs slowly, starting with 100 OSDs ? It's now 1600 placement groups per OSD. What if we chose 30,000 (or 32,768) placement groups to keep room for expansion ? My question is : How will behave a Ceph pool with 1000, 5000 or even 10000 placement groups per OSD ? Will this impact performance ? How bad ? Can it be worked around ? Is this a problem of RAM size ? CPU usage ? Any hint about this would be much appreciated. Thanks ! -- 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
