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Hello, when we started with ceph we wanted to mix different disk-types per host. Since that was before device-classes were available we followed the advice
to create a multi root-hierachy and disk-type-specific hosts. So currently the osd tree looks kind of like this -8 218.21320 root capacity-root -7 36.36887 host ceph-dc-1-01-osd-01-sata-ssd 2 capacity 3.63689 osd.2 up 1.00000 1.00000 9 capacity 3.63689 osd.9 up 1.00000 1.00000 10 capacity 3.63689 osd.10 up 1.00000 1.00000 15 capacity 3.63689 osd.15 up 1.00000 1.00000 20 capacity 3.63689 osd.20 up 1.00000 1.00000 24 capacity 3.63689 osd.24 up 1.00000 1.00000 30 capacity 3.63689 osd.30 up 1.00000 1.00000 33 capacity 3.63689 osd.33 up 1.00000 1.00000 41 capacity 3.63689 osd.41 up 1.00000 1.00000 46 capacity 3.63689 osd.46 up 1.00000 1.00000 -9 36.36887 host ceph-dc-1-01-osd-02-sata-ssd 0 capacity 3.63689 osd.0 up 1.00000 1.00000 1 capacity 3.63689 osd.1 up 1.00000 1.00000 5 capacity 3.63689 osd.5 up 1.00000 1.00000 7 capacity 3.63689 osd.7 up 1.00000 1.00000 12 capacity 3.63689 osd.12 up 1.00000 1.00000 13 capacity 3.63689 osd.13 up 1.00000 1.00000 17 capacity 3.63689 osd.17 up 1.00000 1.00000 18 capacity 3.63689 osd.18 up 1.00000 1.00000 21 capacity 3.63689 osd.21 up 1.00000 1.00000 23 capacity 3.63689 osd.23 up 1.00000 1.00000 …… -73 10.46027 root ssd-root -46 3.48676 host ceph-dc-1-01-osd-01-ssd 38 ssd 0.87169 osd.38 up 1.00000 1.00000 42 ssd 0.87169 osd.42 up 1.00000 1.00000 47 ssd 0.87169 osd.47 up 1.00000 1.00000 61 ssd 0.87169 osd.61 up 1.00000 1.00000 -52 3.48676 host ceph-dc-1-01-osd-02-ssd 40 ssd 0.87169 osd.40 up 1.00000 1.00000 43 ssd 0.87169 osd.43 up 1.00000 1.00000 45 ssd 0.87169 osd.45 up 1.00000 1.00000 49 ssd 0.87169 osd.49 up 1.00000 1.00000 We recently upgrade to luminous (you can see the device-classes in the output). So it should be possible to have one single root, no fake hosts and just
use the device-class. We added some hosts/osds recently which back a new pools, so we also created a new hierarchy and crush rules for those. That worked perfect, and of course
we want to have that for the old parts of the cluster, too Is it possible to move the existing osd’s to a new root/bucket without having to move all the data around (which might be difficult cause we don’t have
enough capacity to move 50 % of the osd’s ) ? I imagine something like: 1.
Magic maintenance command 2.
Move osds to new bucket in hierarchy 3.
Update either existing crush-rule or create new rule an update pool 4.
Magic maintenance-done command We also plan to migrate the ods to bluestore. Should we do this a) before moving b) after moving
I hope our issue is clear. Best regards Carsten
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