> Why would you want to do that? You would want to do that to have minimal data movement, that is, limit the wear on disks to the absolutely necessary minimum. If you replace a disk and re-deploy the OSD with the same ID on the same host with the same device class, only the PGs that land on this OSD will move. If you assign the free IDs randomly, a lot more data movement will occur as the entire crush map will be affected and many more PGs become remapped. Try it on a test cluster. Down an OSD and destroy it. See how many PGs are remapped. When recovery finished, purge the OSD ID. Another huge set of data movement will happen. This second part will happen a second time when adding the disk back and is unnecessary if you plan to replace the disk with an (from ceph point of view) identical disk model. That's why the "destroyed" state for OSDs is there, it keeps the OSD IDs place in the crush map, prevents large data movement on OSD ID removal, can be re-used and then again prevents large data movement on adding (two times the second movement I mentioned above). There was also a bug if OSD IDs are not sequential (there are holed in the ID list). This is fixed, but better safe than sorry. Best regards, ================= Frank Schilder AIT Risø Campus Bygning 109, rum S14 ________________________________________ From: Iztok Gregori <iztok.gregori@xxxxxxxxxx> Sent: Tuesday, July 23, 2024 9:10 AM To: ceph-users@xxxxxxx Subject: Re: How to specify id on newly created OSD with Ceph Orchestrator On 23/07/24 08:41, Robert Sander wrote: > On 7/23/24 08:24, Iztok Gregori wrote: > >> Am I missing something obvious or with Ceph orchestrator there are non >> way to specify an id during the OSD creation? > > Why would you want to do that? For me there wasn't a "real need", I could imagine a scenario in which you want to have a specific osd id range allocated to a specific host, but in my case it is just a curiosity. With "ceph-volume" is possible to specify an id during the OSD creation, but with ceph-orch I didn't find the equivalent option and I'm curious if I've missed something. Cheers Iztok _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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