Hi all, I tested the performance of bluestore in a mixed scene of hdd and ssd. There are three nodes here, each node has 1 mon and 1 mgr 12 osd， Each osd has 1.7T HDD for block, 150G SSD partition for db and wal, 10Gib bond. system： CentOS Linux (3.10.0-862.3.2.el7.x86_64) 7 (Core) ceph version 12.2.5 (cad919881333ac92274171586c827e01f554a70a) luminous (stable) I tested that the performance is very poor and the delay is hug. I found that _kv_sync_thread force_flush took a long time to block the kv commit. so 4krandwrite 32dp IOPS=2469, BW=9878KiB/s lat 12955.49 us. I have some thinking about mixed scene of hdd and ssd： Hdd fdatasync is slow，Can we avoid fdatasync on the wite path（_kv_sync_thread）? batch sync to hdd in the background，For deferred_write can use wal for caching， Is it possible to do a cache on ssd for simple write? Have we had a discussion about the built-in ssd cache for bluestore?-- 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
