Hi Marc,
In general dd isn't the best choice for benchmarking.
In you case there are at least 3 differences from rados bench :
1)If I haven't missed something then you're comparing reads vs. writes
2) Block Size is difference ( 512 bytes for dd vs . 4M for rados bench)
3) Just a single dd instance vs. 16 concurrent threads for rados bench.
Thanks,
Igor
On 8/28/2018 12:50 PM, Marc Roos wrote:
I have a idle test cluster (centos7.5, Linux c04
3.10.0-862.9.1.el7.x86_64), and a client kernel mount cephfs.
I tested reading a few files on this cephfs mount and get very low
results compared to the rados bench. What could be the issue here?
[@client folder]# dd if=5GB.img of=/dev/null status=progress
954585600 bytes (955 MB) copied, 157.455633 s, 6.1 MB/s
I included this is rados bench that shows sort of that cluster
performance is sort of as expected.
[@c01 ~]# rados bench -p fs_data 10 write
hints = 1
Maintaining 16 concurrent writes of 4194304 bytes to objects of size
4194304 for up to 10 seconds or 0 objects
Object prefix: benchmark_data_c01_453883
sec Cur ops started finished avg MB/s cur MB/s last lat(s) avg
lat(s)
0 0 0 0 0 0 -
0
1 16 58 42 167.967 168 0.252071
0.323443
2 16 106 90 179.967 192 0.583383
0.324867
3 16 139 123 163.973 132 0.170865
0.325976
4 16 183 167 166.975 176 0.413676
0.361364
5 16 224 208 166.374 164 0.394369
0.365956
6 16 254 238 158.642 120 0.698396
0.382729
7 16 278 262 149.692 96 0.120742
0.397625
8 16 317 301 150.478 156 0.786822
0.411193
9 16 360 344 152.867 172 0.601956
0.411577
10 16 403 387 154.778 172 0.20342
0.404114
Total time run: 10.353683
Total writes made: 404
Write size: 4194304
Object size: 4194304
Bandwidth (MB/sec): 156.08
Stddev Bandwidth: 29.5778
Max bandwidth (MB/sec): 192
Min bandwidth (MB/sec): 96
Average IOPS: 39
Stddev IOPS: 7
Max IOPS: 48
Min IOPS: 24
Average Latency(s): 0.409676
Stddev Latency(s): 0.243565
Max latency(s): 1.25028
Min latency(s): 0.0830112
Cleaning up (deleting benchmark objects)
Removed 404 objects
Clean up completed and total clean up time :0.867185
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