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Hi all, I run 3 nodes connected with a 10Gbit network, each running 2 OSDs. Disks are 4TB Seagate Constellation ST4000NM0033-9ZM (xfs, journal on same disk). # ceph tell osd.0 bench { "bytes_written": 1073741824, "blocksize": 4194304, "bytes_per_sec": "56494242.000000"} So a single OSD can write up to OSD_BW=55MB/s I have 6 OSDs, so I would expect an overall write bandwidth of: 6*OSD_BW = 6*55 = 330MB/s To verify that, I created a pool with size=1, and run: # rados -p testpool bench 300 write --no-cleanup … Total time run: 300.905982 Total writes made: 13487 Write size: 4194304 Bandwidth (MB/sec): 179.285 Stddev Bandwidth: 106.954 Max bandwidth (MB/sec): 400 Min bandwidth (MB/sec): 0 Average Latency: 0.356925 Stddev Latency: 0.696282 Max latency: 8.5891 Min latency: 0.025648 This is much lower than the expected bandwidth (179 < 330). Is this normal? If so, what is the reason for that? |
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