Hi Amit,
On Mon, 15 Sep 2014, Amit Vijairania wrote:
> Hello!
>
> In a two (2) rack Ceph cluster, with 15 hosts per rack (10 OSD per
> host / 150 OSDs per rack), is it possible to create a ruleset for a
> pool such that the Primary and Secondary PGs/replicas are placed in
> one rack and Tertiary PG/replica is placed in the other rack?
>
> root standard {
> id -1 # do not change unnecessarily
> # weight 734.400
> alg straw
> hash 0 # rjenkins1
> item rack1 weight 367.200
> item rack2 weight 367.200
> }
>
> Given there are only two (2) buckets, but three (3) replica, is it
> even possible?
Yes:
rule myrule {
ruleset 1
type replicated
min_size 1
max_size 10
step take default
step choose firstn 2 type rack
step chooseleaf firstn 2 type host
step emit
}
That will give you 4 osds, spread across 2 hosts in each rack. The pool
size (replication factor) is 3, so RADOS will just use the first three (2
hosts in first rack, 1 host in second rack).
sage
> I think following Giant blueprint is trying to address scenario I
> described above.. Is the following blueprint targeted for Giant
> release?
> http://wiki.ceph.com/Planning/Blueprints/Giant/crush_extension_for_more_flexible_object_placement
>
>
> Regards,
> Amit Vijairania | Cisco Systems, Inc.
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