The pgremapper (and the python one) will allow you to mark all the PGs that a new disk gets as an empty-misplaced PG to be correct where they currently are. This means that after you run one of the remappers, the upmap will tell the cluster to stay as it is even though new empty OSDs have arrived with correct crush weights and all. So you set norebalance, add N+1 new OSDs, the cluster shudders for a short while when the new-empty PGs are created on the new drives, then you have lots and lots of misplaced PGs which norebalance prevents from starting backfills on. Then you run the remapper and "fix" the upmap so all the current placements are considered "correct", and hence the PGs that were supposed to move stop being misplaced. After this, you remove "norebalance" to allow moves to start happening. By now, no movement (or at least very few PGs) should occur. What happens next is that the balancer notices there actually is more space, and figures out the optimal result is more or less the same as above where lots of PGs should go to the new OSDs, but it does this with the max-misplaced-ratio in mind, and it will "move" the PGs by just unsetting their upmap entry that forced them to want to stay in place, so as time passes, it moves a few PGs at a time, and moves them by removing the upmaps from them so that most of the time your other OSDs will look perfectly healthy and will continue to do all the scrubs and things a healthy OSD should do and which it will not do if it has a long queue of backfills waiting to eat up all the slots for non-client IO. While you can do soft additions with increasing crush weights, this potentially causes lots of more movements since an OSD host with OSDs going from 0.1 to 0.2 weight might not place all PGs in the same spot in those two cases, so you could have movement within the host and so on from the recalculated pseudorandom placements on every increase. Den lör 7 sep. 2024 kl 00:15 skrev Eugen Block <eblock@xxxxxx>: > > I can’t say anything about the pgremapper, but have you tried > increasing the crush weight gradually? Add new OSDs with crush initial > weight 0 and then increase it in small steps. I haven’t used that > approach for years, but maybe that can help here. Or are all OSDs > already up and in? Or you could reduce the max misplaced ratio to 1% > or even lower (default is 5%)? > > Zitat von "Szabo, Istvan (Agoda)" <Istvan.Szabo@xxxxxxxxx>: > > > Forgot to paste, somehow I want to reduce this recovery operation: > > recovery: 0 B/s, 941.90k keys/s, 188 objects/s > > To 2-300Keys/sec > > > > > > > > ________________________________ > > From: Szabo, Istvan (Agoda) <Istvan.Szabo@xxxxxxxxx> > > Sent: Friday, September 6, 2024 11:18 PM > > To: Ceph Users <ceph-users@xxxxxxx> > > Subject: Somehow throotle recovery even further than > > basic options? > > > > Hi, > > > > 4 years ago we've created our cluster with all disks 4osds (ssds and > > nvme disks) on octopus. > > The 15TB SSDs still working properly with 4 osds but the small 1.8T > > nvmes with the index pool not. > > Each new nvme osd adding to the existing nodes generates slow ops > > with scrub off, recovery_op_priority 1, backfill and recovery 1-1. > > I even turned off all index pool heavy sync mechanism but the read > > latency still high which means recovery op pushes it even higher. > > > > I'm trying to somehow add resource to the cluster to spread the 2048 > > index pool pg (in replica 3 means 6144pg index pool) but can't make > > it more gentle. > > > > The balancer is working in upmap with max deviation 1. > > > > Have this script from digitalocean > > https://github.com/digitalocean/pgremapper, is there anybody tried > > it before how is it or could this help actually? > > > > Thank you the ideas. > > > > ________________________________ > > This message is confidential and is for the sole use of the intended > > recipient(s). 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