Hi Eugen, Thanks for your insight here. We will go with moving the data to another pool.
Kind Regards From: Eugen Block <[email protected]> Date: Friday, 12 September 2025 at 5:04 pm To: [email protected] <[email protected]> Subject: [EXT] [ceph-users] Re: Is there a faster way to merge PGs? External email: Please exercise caution Hit "send" too soon... I meant to add that apparently, there's no way to increase pg merge. Moving data to a different pool is most likely much faster if you have the capacity (which you seem to have if you want to get rid of 1700 OSDs ;-) ). Zitat von Eugen Block <[email protected]>: > Hi, > > I couldn't find any newer information than this: > >> PG merging works similarly to splitting, except that internally the >> pg_num value is always decreased a single PG at a time. Merging is >> a more complicated and delicate process that requires IO to the PG >> to be paused for a few seconds, and doing merges a single PG at a >> time allows the system to both minimize the impact and simplify the >> overall complexity of the process. > > https://ceph.io/en/news/blog/2019/new-in-nautilus-pg-merging-and-autotuning > > Regards, > Eugen > > Zitat von Justin Mammarella <[email protected]>: > >> Hi folks, >> >> We are in the process of shrinking a CEPH cluster from around 2000 >> osds to 300 osds. >> >> We need to reduce our pg count from 16384 to 8192. >> >> After setting pg_num to 8192, it’s currently it’s taking 3 hours to >> reduce the pool’s PG count by one. >> Which given the number of PGs, will take over 2 years to complete. >> >> Are there any tunables to increase the speed of pg merging? >> >> Our alternative is to create a new pool and transfer the data >> >> Regards, >> >> Justin >> >> >> >> >> >> _______________________________________________ >> ceph-users mailing list -- [email protected] >> To unsubscribe send an email to [email protected] _______________________________________________ ceph-users mailing list -- [email protected] To unsubscribe send an email to [email protected] _______________________________________________ ceph-users mailing list -- [email protected] To unsubscribe send an email to [email protected]
