Hi, we have a cluster with 3 nodes . Each node has 4 HDD and 1 SSD We would like to have a pool only on ssd and a pool only on hdd, using class feature. here is the setup # buckets host ceph01s3 { id -3 # do not change unnecessarily id -4 class hdd # do not change unnecessarily id -21 class ssd # do not change unnecessarily # weight 34.561 alg straw2 hash 0 # rjenkins1 item osd.0 weight 10.914 item osd.5 weight 10.914 item osd.8 weight 10.914 item osd.9 weight 1.819 } host ceph02s3 { id -5 # do not change unnecessarily id -6 class hdd # do not change unnecessarily id -22 class ssd # do not change unnecessarily # weight 34.561 alg straw2 hash 0 # rjenkins1 item osd.1 weight 10.914 item osd.3 weight 10.914 item osd.7 weight 10.914 item osd.10 weight 1.819 } host ceph03s3 { id -7 # do not change unnecessarily id -8 class hdd # do not change unnecessarily id -23 class ssd # do not change unnecessarily # weight 34.561 alg straw2 hash 0 # rjenkins1 item osd.2 weight 10.914 item osd.4 weight 10.914 item osd.6 weight 10.914 item osd.11 weight 1.819 } root default { id -1 # do not change unnecessarily id -2 class hdd # do not change unnecessarily id -24 class ssd # do not change unnecessarily # weight 103.683 alg straw2 hash 0 # rjenkins1 item ceph01s3 weight 34.561 item ceph02s3 weight 34.561 item ceph03s3 weight 34.561 } # rules rule replicated_rule { id 0 type replicated min_size 1 max_size 10 step take default class hdd step chooseleaf firstn 0 type host step emit } rule erasure-code { id 1 type erasure min_size 3 max_size 4 step take default class hdd step set_chooseleaf_tries 5 step set_choose_tries 100 step chooseleaf indep 0 type host step emit } rule erasure2_1 { id 2 type erasure min_size 3 max_size 3 step take default class hdd step set_chooseleaf_tries 5 step set_choose_tries 100 step chooseleaf indep 0 type host step emit } rule erasure-pool.meta { id 3 type erasure min_size 3 max_size 3 step take default class hdd step set_chooseleaf_tries 5 step set_choose_tries 100 step chooseleaf indep 0 type host step emit } rule erasure-pool.data { id 4 type erasure min_size 3 max_size 3 step take default class hdd step set_chooseleaf_tries 5 step set_choose_tries 100 step chooseleaf indep 0 type host step emit } rule replicated_rule_ssd { id 5 type replicated min_size 1 max_size 10 step take default class ssd step chooseleaf firstn 0 type host step emit } # end crush map pool 1 'device_health_metrics' replicated size 3 min_size 2 crush_rule 0 object_hash rjenkins pg_num 1 pgp_num 1 autoscale_mode on last_change 1669 flags hashpspool stripe_width 0 pg_num_max 32 pg_num_min 1 application mgr_devicehealth pool 5 'Datapool' replicated size 3 min_size 2 crush_rule 0 object_hash rjenkins pg_num 32 pgp_num 32 autoscale_mode on last_change 2749 lfor 0/0/321 flags hashpspool,selfmanaged_snaps stripe_width 0 application rbd pool 7 'erasure-pool.data' erasure profile k2m1 size 3 min_size 2 crush_rule 4 object_hash rjenkins pg_num 128 pgp_num 126 pgp_num_target 128 autoscale_mode on last_change 2780 lfor 0/0/1676 flags hashpspool,ec_overwrites stripe_width 8192 application cephfs pool 8 'erasure-pool.meta' replicated size 3 min_size 2 crush_rule 0 object_hash rjenkins pg_num 32 pgp_num 32 autoscale_mode on last_change 344 flags hashpspool stripe_width 0 pg_autoscale_bias 4 pg_num_min 16 recovery_priority 5 application cephfs pool 9 '.rgw.root' replicated size 3 min_size 2 crush_rule 0 object_hash rjenkins pg_num 32 pgp_num 32 autoscale_mode on last_change 592 flags hashpspool stripe_width 0 application rgw pool 10 'brescia-ovest.rgw.log' replicated size 3 min_size 2 crush_rule 0 object_hash rjenkins pg_num 32 pgp_num 32 autoscale_mode on last_change 595 flags hashpspool stripe_width 0 application rgw pool 11 'brescia-ovest.rgw.control' replicated size 3 min_size 2 crush_rule 0 object_hash rjenkins pg_num 32 pgp_num 32 autoscale_mode on last_change 597 flags hashpspool stripe_width 0 application rgw pool 12 'brescia-ovest.rgw.meta' replicated size 3 min_size 2 crush_rule 0 object_hash rjenkins pg_num 8 pgp_num 8 autoscale_mode on last_change 719 lfor 0/719/717 flags hashpspool stripe_width 0 pg_autoscale_bias 4 pg_num_min 8 application rgw pool 13 'brescia-ovest.rgw.buckets.index' replicated size 3 min_size 2 crush_rule 0 object_hash rjenkins pg_num 8 pgp_num 8 autoscale_mode on last_change 845 lfor 0/845/843 flags hashpspool stripe_width 0 pg_autoscale_bias 4 pg_num_min 8 application rgw pool 14 'brescia-ovest.rgw.buckets.data' replicated size 3 min_size 2 crush_rule 0 object_hash rjenkins pg_num 32 pgp_num 32 autoscale_mode on last_change 739 flags hashpspool stripe_width 0 application rgw pool 15 'brescia-ovest.rgw.buckets.non-ec' replicated size 3 min_size 2 crush_rule 0 object_hash rjenkins pg_num 32 pgp_num 32 autoscale_mode on last_change 849 flags hashpspool stripe_width 0 application rgw pool 17 'ssd_pool' replicated size 3 min_size 2 crush_rule 5 object_hash rjenkins pg_num 32 pgp_num 32 autoscale_mode on last_change 2774 lfor 0/0/2653 flags hashpspool stripe_width 0 application rbd rados bench -p ssd_pool 10 write --no-cleanup Object prefix: benchmark_data_ceph01s3.itservicenet.net_268 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 32 16 63.9957 64 0.937457 0.917873 2 16 48 32 63.9936 64 0.882778 0.898646 3 16 64 48 63.9929 64 0.949337 0.903045 4 16 81 65 64.9925 68 0.515819 0.897401 5 16 97 81 64.7919 64 1.00908 0.918797 6 16 114 98 65.3248 68 0.99787 0.922301 7 16 130 114 65.1339 64 0.794492 0.903341 8 16 147 131 65.4909 68 0.770237 0.892833 9 16 173 157 69.7677 104 0.976005 0.878237 10 16 195 179 71.5891 88 0.755363 0.869603 That is very poor ! Why ? Thanks