Shoot for an average, or let the autoscaler handle it with Think of the PG replica count for a given OSD as the share of the workload it will receive. Larger OSDs naturally will receive more workload. # The default is way too low ceph config set global mon_target_pg_per_osd 300 # Instruct the balancer to take smaller bites ceph config set global target_max_misplaced_ratio 0.020000 # Guardrail - when you have varying OSD sizes it's easy to overdose # especially when something fails. This does not affect placement, but it # prevents awkward failures of PGs to activate. ceph config set global mon_max_pg_per_osd 1000 # Varying OSD sizes can result in suboptimal balancing by default mgr/balancer/upmap_max_deviation 1 Your list of sizes impliess that you have both mixed-use 3DWPD SSDs and read-intensive 1DWPD SSDs. Is this intentional? I've yet to see a Ceph deployment that indicated the extra cost of MU SSDs, which are the same hardware as RI SSDs, just with a different overprovisioning setting.

On Aug 7, 2025, at 8:08 AM, Albert Shih <Albert.Shih@obspm.fr> wrote:

Hi,

Stupid question but how can I set the number of pg for a pool when I got differents (1.7 To , 2.7T, 2.9To and 3.4To) size of ssd ?

Regards -- Albert SHIH 🦫 🐸 France Heure locale/Local time: jeu. 07 août 2025 14:06:35 CEST _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io