>
> VM don't do many writes and i migrated main testing VM's to 2TB pool which
> in turns fragments faster.
>
>
> Did a lot of tests and recreated pools and OSD's in many ways but in a
> matter of days every time each OSD's gets severely fragmented and loses up
> to 80% of write performance (tested with many FIO tests , rados benches ,
> osd benches , RBD benches).
Where is the rados bench before and after your problem?
>
> If i delete the osd's from node and let it sync from 2 nodes it will be
> perfect for a few days 0.1 - 0.2 bluestore fragmentation but then it is in
> 0.8+ state soon.
What makes you think that this is the cause of your problem?
> [SPOILER="CEPH bluestore fragmentation"]
>
> [CODE]osd.3 "fragmentation_rating": 0.090421032864104897
>
> osd.10 "fragmentation_rating": 0.093359029842755931
>
> osd.7 "fragmentation_rating": 0.083908842581664561
>
> osd.8 "fragmentation_rating": 0.067356428512611116
>
>
> after 5 days
>
>
> osd.3 "fragmentation_rating": 0.2567613553223777
>
> osd.10 "fragmentation_rating": 0.25025098722978778
>
> osd.7 "fragmentation_rating": 0.77481281469969676
>
> osd.8 "fragmentation_rating": 0.82260745733487917
>
>
> after few weeks
>
>
> 0,882571391878622
>
> 0,891192311159292
>
I have the same after >year or so, my performance seems to be the same (running
ceph 14)
[@~]# ceph daemon osd.39 bluestore allocator score block
{
"fragmentation_rating": 0.88113008621473943
}
>
>
> osd.0: {
>
> "bytes_written": 1073741824,
>
> "blocksize": 4194304,
>
> "elapsed_sec": 0.41652934400000002,
>
> "bytes_per_sec": 2577829964.3638072,
>
> "iops": 614.60255726905041
>
> }
>
>
>
> IOPS in osd bench after some time go to as low as 108 with 455MB/s
To me this looks like normal sequential write performance to an ssd.
my ssd:
[@c01 ~]# ceph tell osd.39 bench
{
"bytes_written": 1073741824,
"blocksize": 4194304,
"elapsed_sec": 2.4248152520000001,
"bytes_per_sec": 442813869.26875037,
"iops": 105.57505351752052
}
>
> I noticed posts on the internet asking how to prevent or fix fragmentation
> but no replies to them and RedHat CEPH documentation says "to call Redhat
> to assist with fragmentation."
>
> Anyone knows what causes fragmentation and how to solve it without
> deleting
>
I am curious what makes you think this is related to the 'fragmentation_rating'
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