You talked about "using default settings wherever possible"... Well, Ceph's default settings everywhere they exist, is to not allow you to write while you don't have at least 1 more copy that you can lose without data loss. If your bosses require you to be able to lose 2 servers and still serve customers, then tell them that Ceph requires you to have 3 parity copies of the data.
Why do you want to change your one and only copy of the data while you already have a degraded system? And not just a degraded system, but a system where 2/5's of your servers are down... That sounds awful, terrible, and just plain bad. To directly answer your question about min_size, min_size does not affect where data is placed. It only affects when a PG claims to not have enough copies online to be able to receive read or write requests. On Tue, May 8, 2018 at 7:47 AM Janne Johansson <icepic...@gmail.com> wrote: > 2018-05-08 1:46 GMT+02:00 Maciej Puzio <mkp37...@gmail.com>: > >> Paul, many thanks for your reply. >> Thinking about it, I can't decide if I'd prefer to operate the storage >> server without redundancy, or have it automatically force a downtime, >> subjecting me to a rage of my users and my boss. >> But I think that the typical expectation is that system serves the >> data while it is able to do so. > > > If you want to prevent angry bosses, you would have made 10 OSD hosts > or some other large number so that ceph cloud place PGs over more places > so that 2 lost hosts would not impact so much, but also so it can recover > into > each PG into one of the 10 ( minus two broken minus the three that already > hold data you want to spread out) other OSDs and get back into full service > even with two lost hosts. > > It's fun to test assumptions and "how low can I go", but if you REALLY > wanted > a cluster with resilience to planned and unplanned maintenance, > you would have redundancy, just like that Raid6 disk box would > presumably have a fair amount of hot and perhaps cold spares nearby to kick > in if lots of disks started go missing. > > -- > May the most significant bit of your life be positive. > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >
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