Rados bench before deleting OSD's and recreating them + syncing with
fragmentation 0.89

>  T1 - wr,4M
> Total time run         60.0405
> Total writes made      9997
> Write size             4194304
> Object size            4194304
> Bandwidth (MB/sec) 666,017
> Stddev Bandwidth       24.1108
> Max bandwidth (MB/sec) 744
> Min bandwidth (MB/sec) 604
> Average IOPS           166
> Stddev IOPS            6.02769
> Max IOPS               186
> Min IOPS               151
> Average Latency(s)     0.0960791
> Stddev Latency(s)      0.0182781
> Max latency(s)         0.190993
> Min latency(s)         0.0284014


 T2 = ro,seq,4M
> Total time run 250.486
> Total reads made 9997
> Read size 4194304
> Object size 4194304
> Bandwidth (MB/sec) 1596,41
> Average IOPS 399
> Stddev IOPS 252.166
> Max IOPS 446
> Min IOPS 350
> Average Latency(s)   0.0395391
> Max latency(s)       0.187176
> Min latency(s)       0.0056981


 T3 = ro,rand,4M
> Total time run 600.463
> Total reads made 23.947
> Read size 4194304
> Object size 4194304
> Bandwidth (MB/sec) 1595,24
> Average IOPS 398
> Stddev IOPS 261.614
> Max IOPS 446
> Min IOPS 341
> Average Latency(s)   0.0395782
> Max latency(s)       0.17207
> Min latency(s)       0.00326339



Rados bench after recreating and sync with fragmentation 0.1

 T1
> Total time run         60.0143
> Total writes made      30868
> Write size             4194304
> Object size            4194304
> Bandwidth (MB/sec) 2057,38
> Stddev Bandwidth 121.141
> Max bandwidth (MB/sec) 2208
> Min bandwidth (MB/sec) 1472
> Average IOPS           514
> Stddev IOPS            30.2852
> Max IOPS               552
> Min IOPS               368
> Average Latency(s)     0.0310978
> Stddev Latency(s)      0.0120903
> Max latency(s)         0.127144
> Min latency(s)         0.00719787


 T2
> Total time run       51.9554
> Total reads made     30868
> Read size            4194304
> Object size          4194304
> Bandwidth (MB/sec) 2376,5
> Average IOPS 594
> Stddev IOPS          27.1142
> Max IOPS             641
> Min IOPS             543
> Average Latency(s)   0.026446
> Max latency(s)       0.120386
> Min latency(s)       0.00436071


T3
> Total time run       60.0455
> Total reads made     33853
> Read size            4194304
> Object size          4194304
> Bandwidth (MB/sec) 2255,16
> Average IOPS 563
> Stddev IOPS          23.7633
> Max IOPS             616
> Min IOPS             500
> Average Latency(s)   0.0278983
> Max latency(s)       0.13513
> Min latency(s)       0.00267677


> To me this looks like normal sequential write performance to an ssd.

This is normal write for these OSD's when they are not fragmented and
already have data , osd bench:

> Server disk osd MB/s IOPS
> s01 2TB osd.7 2.587 616
> s01 2TB osd.8 2.566 611
> s02 2TB osd.2 2.611 622
> s02 2TB osd.6 2.555 609
> s03 2TB osd.0 2.519 600
> s03 2TB osd.1 2.552 608
> s01 4TB osd.3 3.319 791
> s01 4TB osd.10 4.054 966
> s02 4TB osd.4 3.884 926
> s02 4TB osd.11 3.931 937
> s03 4TB osd.5 3.797 905
> s03 4TB osd.9 3.701 882




and this is when it is fragmented , first 3 are on 2TB drives OSD's and
second 3 on 4TB

MB/s IOPS
> 455 108
> 449 107
> 533 127
> 846 201
> 825 196
> 795 189


> I am curious what makes you think this is related to the
'fragmentation_rating'

I did hundreds of fio tests , rados , osd benches etc and recreated OSD's
many times with different number of OSD's , PG's etc and only thing that is
constant is this fragmentation that happens after few days of light use and
all performance in all tests follows it.
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