I have a Mimic Bluestore EC RBD Pool running on 8+2, this is currently running across 4 node's.
3 Node's are running Toshiba disk's while one node is running Segate disks (same size, spinning speed, enterprise disks e.t.c), I have noticed huge difference in IOWAIT and disk latency performance between the two sets of disks, can also be seen from a ceph osd perf during read and write operations. Speaking to my host (server provider), they bench marked the two disks before approving them for use in this type of server, they actually saw higher performance from the Toshiba disk during their tests. They did however state there test where at higher / larger block sizes, I can imagine CEPH using EC of 8+2 the block sizes / requests are quite small? Is there anything I can do ? Changing the RBD object size & stripe unit to a bigger than default? Will this make the data sent to the disk larger chunks at once compared to lot's of smaller block's. If anyone else has any advice I'm open to trying. P.s I have already disabled the disk cache on all disks and this was causing high write latency across all. Thanks
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