Hi,Janne Thank you for correcting my mistake. Maybe the first advice description is unclear,I want to say that add osds into one failuer domain at a time , so that only one PG among up set to remap at a time. -------------- zhanrzh_xt@xxxxxxxxxxxxxx >Den tors 25 juli 2019 kl 10:47 skrev 展荣臻（信泰） <zhanrzh_xt@xxxxxxxxxxxxxx>: > >> >> 1、Adding osds in same one failure domain is to ensure only one PG in pg up >> set (ceph pg dump shows)to remap. >> 2、Setting "osd_pool_default_min_size=1" is to ensure objects to read/write >> uninterruptedly while pg remap. >> Is this wrong? >> > >How did you read the first email where he described how 3 copies was not >enough, wanting to perhaps go to 4 copies >to make sure he is not putting data at risk? > >The effect you describe is technically correct, it will allow writes to >pass, but it would also go 100% against what ceph tries to do here, retain >the data even while doing planned maintenance, even while getting >unexpected downtime. > >Setting min_size=1 means you don't care at all for your data, and that you >will be placing it under extreme risks. > >Not only will that single copy be a danger, but you can easily get into a >situation where your singlecopy-write gets accepted and then that drive >gets destroyed, and the cluster will know the latest writes ended up on it, >and even getting the two older copies back will not help, since it has >already registered that somewhere there is a newer version. For a single >object, reverting to older (if possible) isn't all that bad, but for a >section in the middle of a VM drive, that could mean total disaster. > >There are lots of people losing data with 1 copy, lots of posts on how >repl_size=2, min_size=1 lost data for people using ceph, so I think posting >advice to that effect goes against what ceph is good for. > >Not that I think the original poster would fall into that trap, but others >might find this post later and think that it would be a good solution to >maximize risk while adding/rebuilding 100s of OSDs. I don't agree. > > >> Den tors 25 juli 2019 kl 04:36 skrev zhanrzh_xt@xxxxxxxxxxxxxx < >> zhanrzh_xt@xxxxxxxxxxxxxx>: >> >>> I think it should to set "osd_pool_default_min_size=1" before you add osd >>> , >>> and the osd that you add at a time should in same Failure domain. >>> >> >> That sounds like weird or even bad advice? >> What is the motivation behind it? >> >> >-- >May the most significant bit of your life be positive. _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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