* I don’t follow; adding new OSDs should on average decrease the PG replicas on the existing OSDs. But imbalances during topology changes are one reason I like to raise mon_max_pg_per_osd to 1000, otherwise you can end up with PGs that won’t activate. Yeah, have a look here: https://ibb.co/WVq3hNr This time the existing osd on the same host got a spike with other pgs which is not good 😕 after it slowly goes down. This is the node in the crush tree: -37 118.75211 host osd-2s12 440 nvme 0.43660 osd.440 up 1.00000 1.00000 441 nvme 0.43660 osd.441 up 1.00000 1.00000 442 nvme 0.43660 osd.442 up 1.00000 1.00000 443 nvme 0.43660 osd.443 up 1.00000 1.00000 444 nvme 0.43660 osd.444 up 1.00000 1.00000 445 nvme 0.43660 osd.445 up 1.00000 1.00000 446 nvme 0.43660 osd.446 up 1.00000 1.00000 447 nvme 0.43660 osd.447 up 1.00000 1.00000 596 nvme 1.74660 osd.596 up 0.50000 1.00000 597 nvme 1.74660 osd.597 up 0.50000 1.00000 440-447 are 2x 1.7TB nvmes with 4 osds on those. 596-597 is the newly added 3.8TB nvme disk with 2 osd to spread the pgs somehow on the node. I want to remove to be honest all the 4osd/nvme from the cluster and have only 1x osd on those 1.7TB nvmes but first I need space for the pgs so I think better to add first the nvmes rather than remove and reprovision. Or maybe I should reweight to 0 all of them and make a clear node without nvme, then add all the nvmes back to the node? Not sure extension or removal is the better option. ________________________________ From: Anthony D'Atri <anthony.datri@xxxxxxxxx> Sent: Saturday, September 7, 2024 9:35 AM To: Szabo, Istvan (Agoda) <Istvan.Szabo@xxxxxxxxx> Cc: Eugen Block <eblock@xxxxxx>; ceph-users@xxxxxxx <ceph-users@xxxxxxx> Subject: Re: Somehow throotle recovery even further than basic options? Email received from the internet. If in doubt, don't click any link nor open any attachment ! ________________________________ > This sounds interesting because this way the pressure wouldn't be too big if go like 0.1 0.2 OSD by OSD. I used to do this as well, back before pg-upmap was a thing, and while I still had Jewel clients. It is however less efficient, because some data ends up moving more than once. Upweighting a handful of OSDs at the same time may spread the load and allow faster progress than going one at a time. Say one per host or one per failure domain. The PG remapping tools allow fine-grained control with more efficiency, though any clients that aren’t Luminous or later will have a really bad day. > What I can see how ceph did it, when add the new OSDs, the complete host get the remapped pgs from other hosts also, so the old osds PG number increased by like +50% (which was already overloaded) and slowly rebalance to the newly added osds on the same host. This initial pressure to big. I don’t follow; adding new OSDs should on average decrease the PG replicas on the existing OSDs. But imbalances during topology changes are one reason I like to raise mon_max_pg_per_osd to 1000, otherwise you can end up with PGs that won’t activate. > > This "misplaced ratio to 1%" I've never tried, let me read a bit, thank you. > > Istvan > ________________________________ > From: Eugen Block <eblock@xxxxxx> > Sent: Saturday, September 7, 2024 4:55:40 AM > To: ceph-users@xxxxxxx <ceph-users@xxxxxxx> > Subject: Re: Somehow throotle recovery even further than basic options? > > Email received from the internet. If in doubt, don't click any link nor open any attachment ! > ________________________________ > > 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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