How are you mounting CephFS? It may be that the cache settings are just set very badly for a 10G pipe. Plus rados bench is a very parallel large-IO benchmark and many benchmarks you might dump into a filesystem are definitely not.
-Greg
Hi,
I have a cluster serving cephfs and it works. It’s just slow. Client is using the kernel driver. I can ‘rados bench’ writes to the cephfs_data pool at wire speeds (9580Mb/s on a 10G link) but when I copy data into cephfs it is rare to get above 100Mb/s. Large file writes may start fast (2Gb/s) but within a minute slows. In the dashboard at the OSDs I get lots of triangles (it doesn't stream) which seems to be lots of starts and stops. By contrast the graphs show constant flow when using 'rados bench.'
I feel like I'm missing something obvious. What can I do to help diagnose this better or resolve the issue?
Errata:
Version: 12.2.7 (on everything)
mon: 3 daemons, quorum cephmon-s01,cephmon-s03,cephmon-s02
mgr: cephmon-s02(active), standbys: cephmon-s01, cephmon-s03
mds: cephfs1-1/1/1 up {0=cephmon-s02=up:active}, 2 up:standby
osd: 70 osds: 70 up, 70 in
rgw: 3 daemons active
rados bench summary:
Total time run: 600.043733
Total writes made: 167725
Write size: 4194304
Object size: 4194304
Bandwidth (MB/sec): 1118.09
Stddev Bandwidth: 7.23868
Max bandwidth (MB/sec): 1140
Min bandwidth (MB/sec): 1084
Average IOPS: 279
Stddev IOPS: 1
Max IOPS: 285
Min IOPS: 271
Average Latency(s): 0.057239
Stddev Latency(s): 0.0354817
Max latency(s): 0.367037
Min latency(s): 0.0120791
peter
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