[PVE-User] Proxmox HCI Ceph: "osd_max_backfills" is overridden and set to 1000

[Benjamin Hofer]

Dear community,

We've set up a Proxmox hyper-converged Ceph cluster in production.
After syncing in one new OSD using the "pveceph osd create" command,
we got massive network performance issues and outages. We then found
that "osd_max_backfills" is set to 1000 (Ceph default is 1) and that
this (along with some other values) have been overridden.

Does anyone know a root cause? I can't imagine that this is the
Proxmox default behaviour and I'm very sure that we didn't change
anything (actually I didn't even know the value before researching and
talking to colleagues with deeper Ceph knowledge).

System:

PVE version output: pve-manager/7.3-6/723bb6ec (running kernel: 5.15.102-1-pve)
ceph version 17.2.5 (e04241aa9b639588fa6c864845287d2824cb6b55) quincy (stable)

# ceph config get osd.1
WHO    MASK  LEVEL  OPTION                            VALUE         RO
osd.1        basic  osd_mclock_max_capacity_iops_ssd  17080.220753

# ceph config show osd.1
NAME                                             VALUE
            SOURCE    OVERRIDES  IGNORES
auth_client_required                             cephx
            file
auth_cluster_required                            cephx
            file
auth_service_required                            cephx
            file
cluster_network                                  10.0.18.0/24
            file
daemonize                                        false
            override
keyring                                          $osd_data/keyring
            default
leveldb_log
            default
mon_allow_pool_delete                            true
            file
mon_host                                         10.0.18.30 10.0.18.10
10.0.18.20  file
ms_bind_ipv4                                     true
            file
ms_bind_ipv6                                     false
            file
no_config_file                                   false
            override
osd_delete_sleep                                 0.000000
            override
osd_delete_sleep_hdd                             0.000000
            override
osd_delete_sleep_hybrid                          0.000000
            override
osd_delete_sleep_ssd                             0.000000
            override
osd_max_backfills                                1000
            override
osd_mclock_max_capacity_iops_ssd                 17080.220753
            mon
osd_mclock_scheduler_background_best_effort_lim  999999
            default
osd_mclock_scheduler_background_best_effort_res  534
            default
osd_mclock_scheduler_background_best_effort_wgt  2
            default
osd_mclock_scheduler_background_recovery_lim     2135
            default
osd_mclock_scheduler_background_recovery_res     534
            default
osd_mclock_scheduler_background_recovery_wgt     1
            default
osd_mclock_scheduler_client_lim                  999999
            default
osd_mclock_scheduler_client_res                  1068
            default
osd_mclock_scheduler_client_wgt                  2
            default
osd_pool_default_min_size                        2
            file
osd_pool_default_size                            3
            file
osd_recovery_max_active                          1000
            override
osd_recovery_max_active_hdd                      1000
            override
osd_recovery_max_active_ssd                      1000
            override
osd_recovery_sleep                               0.000000
            override
osd_recovery_sleep_hdd                           0.000000
            override
osd_recovery_sleep_hybrid                        0.000000
            override
osd_recovery_sleep_ssd                           0.000000
            override
osd_scrub_sleep                                  0.000000
            override
osd_snap_trim_sleep                              0.000000
            override
osd_snap_trim_sleep_hdd                          0.000000
            override
osd_snap_trim_sleep_hybrid                       0.000000
            override
osd_snap_trim_sleep_ssd                          0.000000
            override
public_network                                   10.0.18.0/24
            file
rbd_default_features                             61
            default
rbd_qos_exclude_ops                              0
            default
setgroup                                         ceph
            cmdline
setuser                                          ceph
            cmdline

Thanks a lot in advance.

Best
Benjamin