Hi,

Any idea why 2 servers with one OSD each will provide better performance
than 3 ?

Servers are identical
Performance  is impacted irrespective if I used SSD for WAL/DB or not
Basically, I am getting lots of cur MB/s zero

Network is separate 10 GB for public and private
I tested it with iperf and I am getting 9.3 Gbs

I have tried replication by 2 and 3 with same results ( much better for 2
servers than 3 )

reinstalled CEPH multiple times
ceph.conf very simple - no major customization ( see below)
I am out of ideas - any hint will be TRULY appreciated

Steven



auth_cluster_required = cephx
auth_service_required = cephx
auth_client_required = cephx


public_network = 10.10.30.0/24
cluster_network = 192.168.0.0/24


osd_pool_default_size = 2
osd_pool_default_min_size = 1 # Allow writing 1 copy in a degraded state
osd_crush_chooseleaf_type = 1


[mon]
mon_allow_pool_delete = true
mon_osd_min_down_reporters = 1

[osd]
osd_mkfs_type = xfs
osd_mount_options_xfs =
"rw,noatime,nodiratime,attr2,logbufs=8,logbsize=256k,largeio,inode64,swalloc,allocsize=4M"
osd_mkfs_options_xfs = "-f -i size=2048"
bluestore_block_db_size = 32212254720
bluestore_block_wal_size = 1073741824

rados bench -p rbd 120 write --no-cleanup && rados bench -p rbd 120 seq
hints = 1
Maintaining 16 concurrent writes of 4194304 bytes to objects of size
4194304 for up to 120 seconds or 0 objects
Object prefix: benchmark_data_osd01_383626
  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        57        41   163.991       164    0.197929
0.065543
    2      16        57        41    81.992         0           -
0.065543
    3      16        67        51   67.9936        20   0.0164632
0.249939
    4      16        67        51   50.9951         0           -
0.249939
    5      16        71        55   43.9958         8   0.0171439
0.319973
    6      16       181       165   109.989       440   0.0159057
0.563746
    7      16       182       166   94.8476         4    0.221421
0.561684
    8      16       182       166   82.9917         0           -
0.561684
    9      16       240       224   99.5458       116   0.0232989
0.638292
   10      16       264       248   99.1901        96   0.0222669
0.583336
   11      16       264       248   90.1729         0           -
0.583336
   12      16       285       269   89.6579        42   0.0165706
0.600606
   13      16       285       269   82.7611         0           -
0.600606
   14      16       310       294   83.9918        50   0.0254241
0.756351
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