Hi list,

I'm trying to get the best from my 3 node "low cost" hardware for testing 
purposes :
3 Dell PowerEdge 2950.
Cluster/Public networks both with 2x1Gb LACP (layer3+4 hash)
No MDS running for now.
SAS disks (no ssd), both 10000 & 15000 rpm.
Sda = system
Sdb, sdc, sdd, sde = OSDs
Sdf = journal (osd_journal_size = 1024)

My question is how can I optimize my osd weights (or something else) regarding 
my config ? is the hdparm -t test below useful do to so ? For instance, is it a 
better choice to use sdd for journals ?

Some quick tests :

ceph1:
hdparm -t /dev/sdb ; hdparm -t /dev/sdc ; hdparm -t /dev/sdd ; hdparm -t 
/dev/sde ; hdparm -t /dev/sdf
/dev/sdb:
Timing buffered disk reads: 374 MB in  3.00 seconds = 124.62 MB/sec
/dev/sdc:
Timing buffered disk reads: 264 MB in  3.02 seconds =  87.51 MB/sec
/dev/sdd:
Timing buffered disk reads: 470 MB in  3.01 seconds = 156.19 MB/sec
/dev/sde:
Timing buffered disk reads: 264 MB in  3.01 seconds =  87.61 MB/sec
/dev/sdf:
Timing buffered disk reads: 268 MB in  3.01 seconds =  89.00 MB/sec

ceph2:
hdparm -t /dev/sdb ; hdparm -t /dev/sdc ; hdparm -t /dev/sdd ; hdparm -t 
/dev/sde ; hdparm -t /dev/sdf
/dev/sdb:
Timing buffered disk reads: 376 MB in  3.00 seconds = 125.15 MB/sec
/dev/sdc:
Timing buffered disk reads: 264 MB in  3.01 seconds =  87.68 MB/sec
/dev/sdd:
Timing buffered disk reads: 502 MB in  3.01 seconds = 166.71 MB/sec
/dev/sde:
Timing buffered disk reads: 264 MB in  3.02 seconds =  87.55 MB/sec
/dev/sdf:
Timing buffered disk reads: 268 MB in  3.01 seconds =  89.09 MB/sec

ceph3:
hdparm -t /dev/sdb ; hdparm -t /dev/sdc ; hdparm -t /dev/sdd ; hdparm -t 
/dev/sde ; hdparm -t /dev/sdf
/dev/sdb:
Timing buffered disk reads: 376 MB in  3.00 seconds = 125.14 MB/sec
/dev/sdc:
Timing buffered disk reads: 236 MB in  3.00 seconds =  78.64 MB/sec
/dev/sdd:
Timing buffered disk reads: 504 MB in  3.00 seconds = 167.77 MB/sec
/dev/sde:
Timing buffered disk reads: 258 MB in  3.01 seconds =  85.66 MB/sec
/dev/sdf:
Timing buffered disk reads: 274 MB in  3.00 seconds =  91.28 MB/sec

Some test now with dd and rados bench on rbd client mountpoint :

rados bench -p logs 100 write

Total time run:        101.479343
Total writes made:     1626
Write size:            4194304
Bandwidth (MB/sec):    64.092

Average Latency:       0.996858
Max latency:           3.23692
Min latency:           0.106049


rados bench -p logs 100 seq

Total time run:        35.625185
Total reads made:     1626
Read size:            4194304
Bandwidth (MB/sec):    182.567

Average Latency:       0.350297
Max latency:           1.5221
Min latency:           0.048679


DD on a remote rbd mountpoint:
dd if=/dev/zero of=here bs=1G count=1 oflag=direct
1+0 records in
1+0 records out
1073741824 bytes (1.1 GB) copied, 16.8977 s, 63.5 MB/s

dd if=/dev/zero of=here bs=200M count=100 oflag=direct
100+0 records in
100+0 records out
20971520000 bytes (21 GB) copied, 341.549 s, 61.4 MB/s

And my crushmap :
# begin crush map

# devices
device 0 osd.0
device 1 osd.1
device 2 osd.2
device 3 osd.3
device 4 osd.4
device 5 osd.5
device 6 osd.6
device 7 osd.7
device 8 osd.8
device 9 osd.9
device 10 osd.10
device 11 osd.11

# types
type 0 osd
type 1 host
type 2 rack
type 3 row
type 4 room
type 5 datacenter
type 6 root

# buckets
host ceph1 {
      id -2       # do not change unnecessarily
      # weight 0.880
      alg straw
      hash 0      # rjenkins1
      item osd.0 weight 0.070
      item osd.1 weight 0.270
      item osd.2 weight 0.270
      item osd.3 weight 0.270
}
host ceph2 {
      id -3       # do not change unnecessarily
      # weight 0.880
      alg straw
      hash 0      # rjenkins1
      item osd.4 weight 0.070
      item osd.5 weight 0.270
      item osd.6 weight 0.270
      item osd.7 weight 0.270
}
host ceph3 {
      id -4       # do not change unnecessarily
      # weight 0.880
      alg straw
      hash 0      # rjenkins1
      item osd.8 weight 0.070
      item osd.9 weight 0.270
      item osd.10 weight 0.270
      item osd.11 weight 0.270
}
root default {
      id -1       # do not change unnecessarily
      # weight 2.640
      alg straw
      hash 0      # rjenkins1
      item ceph1 weight 0.880
      item ceph2 weight 0.880
      item ceph3 weight 0.880
}

# rules
rule data {
      ruleset 0
      type replicated
      min_size 1
      max_size 10
      step take default
      step chooseleaf firstn 0 type host
      step emit
}
rule metadata {
      ruleset 1
      type replicated
      min_size 1
      max_size 10
      step take default
      step chooseleaf firstn 0 type host
      step emit
}
rule rbd {
      ruleset 2
      type replicated
      min_size 1
      max_size 10
      step take default
      step chooseleaf firstn 0 type host
      step emit
}

# end crush map





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