On Wed, Feb 20, 2013 at 12:39 PM, Sage Weil <sage@xxxxxxxxxxx> wrote:
> On Wed, 20 Feb 2013, Bo-Syung Yang wrote:
>> Hi,
>>
>> I have a crush map (may not be practical, but just for demo) applied
>> to a two-host cluster (each host has two OSDs) to test "ceph osd crush
>> reweight":
>>
>> # begin crush map
>>
>> # devices
>> device 0 sdc-host0
>> device 1 sdd-host0
>> device 2 sdc-host1
>> device 3 sdd-host1
>>
>> # types
>> type 0 device
>> type 1 pool
>> type 2 root
>>
>> # buckets
>> pool one {
>> id -1
>> alg straw
>> hash 0 # rjenkins1
>> item sdc-host0 weight 1.000
>> item sdd-host0 weight 1.000
>> item sdc-host1 weight 1.000
>> item sdd-host1 weight 1.000
>> }
>>
>> pool two {
>> id -2
>> alg straw
>> hash 0 # rjenkins1
>> item sdc-host0 weight 1.000
>> item sdd-host0 weight 1.000
>> item sdc-host1 weight 1.000
>> item sdd-host1 weight 1.000
>> }
>>
>> root root-for-one {
>> id -3
>> alg straw
>> hash 0 # rjenkins1
>> item one weight 4.000
>> item two weight 4.000
>> }
>>
>> root root-for-two {
>> id -4
>> alg straw
>> hash 0 # rjenkins1
>> item one weight 4.000
>> item two weight 4.000
>> }
>>
>> rule data {
>> ruleset 0
>> type replicated
>> min_size 1
>> max_size 4
>> step take root-for-one
>> step choose firstn 0 type pool
>> step choose firstn 1 type device
>> step emit
>> }
>>
>> rule metadata {
>> ruleset 1
>> type replicated
>> min_size 1
>> max_size 4
>> step take root-for-one
>> step choose firstn 0 type pool
>> step choose firstn 1 type device
>> step emit
>> }
>>
>> rule rbd {
>> ruleset 2
>> type replicated
>> min_size 1
>> max_size 4
>> step take root-for-two
>> step choose firstn 0 type pool
>> step choose firstn 1 type device
>> step emit
>> }
>>
>>
>> After crush map applied, the osd tree looks as:
>>
>> # id weight type name up/down reweight
>> -4 8 root root-for-two
>> -1 4 pool one
>> 0 1 osd.0 up 1
>> 1 1 osd.1 up 1
>> 2 1 osd.2 up 1
>> 3 1 osd.3 up 1
>> -2 4 pool two
>> 0 1 osd.0 up 1
>> 1 1 osd.1 up 1
>> 2 1 osd.2 up 1
>> 3 1 osd.3 up 1
>> -3 8 root root-for-one
>> -1 4 pool one
>> 0 1 osd.0 up 1
>> 1 1 osd.1 up 1
>> 2 1 osd.2 up 1
>> 3 1 osd.3 up 1
>> -2 4 pool two
>> 0 1 osd.0 up 1
>> 1 1 osd.1 up 1
>> 2 1 osd.2 up 1
>> 3 1 osd.3 up 1
>>
>>
>> Then, I reweight osd.0 (device sdc-host0) in crush map to 5 through:
>>
>> ceph osd crush reweight sdc-host0 5
>>
>> I found the osd tree with the weight changes:
>>
>> # id weight type name up/down reweight
>> -4 8 root root-for-two
>> -1 4 pool one
>> 0 5 osd.0 up 1
>> 1 1 osd.1 up 1
>> 2 1 osd.2 up 1
>> 3 1 osd.3 up 1
>> -2 4 pool two
>> 0 1 osd.0 up 1
>> 1 1 osd.1 up 1
>> 2 1 osd.2 up 1
>> 3 1 osd.3 up 1
>> -3 12 root root-for-one
>> -1 8 pool one
>> 0 5 osd.0 up 1
>> 1 1 osd.1 up 1
>> 2 1 osd.2 up 1
>> 3 1 osd.3 up 1
>> -2 4 pool two
>> 0 1 osd.0 up 1
>> 1 1 osd.1 up 1
>> 2 1 osd.2 up 1
>> 3 1 osd.3 up 1
>>
>> My question is why only pool one's weight changed, but not pool two.
>
> Currently the reweight (and most of the other) command(s) assume there is
> only one instance of each item in the hierarchy, and only operate on the
> first one they see.
>
> What is your motivation for having the pools appear in two different
> trees?
>
> sage
>
By defining different pools in different trees, it allows me setting
different rules for sharing certain OSDs or/and isolating the others
for the different pools (created through ceph osd pool create ...)
Thanks,
Edward
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