Thanks Sage! We will test this and share our observations..
Regards,
Amit
Amit Vijairania | 415.610.9908
--*--
On Mon, Sep 15, 2014 at 8:28 AM, Sage Weil <sweil at redhat.com> wrote:
> 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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>>
