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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