On Thu, Aug 24, 2017 at 6:44 PM, David Turner <drakonstein@xxxxxxxxx> wrote:
>> min_size 1
> STOP THE MADNESS. Search the ML to realize why you should never user a
> min_size of 1.
This is a (completely understandable) misunderstanding. The
"min_size" in a crush rule is a different thing to the min_size in a
pool. In a crush rule, the min_size/max_size parameters are just
declaring a range of pool sizes to which the rule may be applied.
This is a legacy thing from when we had "rule sets" with multiple
rules, and pools were given a rule set, then the rule's
min_size/max_size where used to decide which rule in a rule set should
apply to a given pool, based on the pool's size.
I think we still have the field for backward compatibility with
systems that might have had interesting ruleset configurations, but
now is probably a good time to look at trying to find a way to rip it
out or at least hide it.
John
>
> I'm curious as well as to what this sort of configuration will do for how
> many copies are stored between DCs.
>
> On Thu, Aug 24, 2017 at 1:03 PM Sinan Polat <sinan@xxxxxxxx> wrote:
>>
>> Hi,
>>
>>
>>
>> In a Multi Datacenter Cluster I have the following rulesets:
>>
>> ------------------
>>
>> rule ams5_ssd {
>>
>> ruleset 1
>>
>> type replicated
>>
>> min_size 1
>>
>> max_size 10
>>
>> step take ams5-ssd
>>
>> step chooseleaf firstn 2 type host
>>
>> step emit
>>
>> step take ams6-ssd
>>
>> step chooseleaf firstn -2 type host
>>
>> step emit
>>
>> }
>>
>> rule ams6_ssd {
>>
>> ruleset 2
>>
>> type replicated
>>
>> min_size 1
>>
>> max_size 10
>>
>> step take ams6-ssd
>>
>> step chooseleaf firstn 2 type host
>>
>> step emit
>>
>> step take ams5-ssd
>>
>> step chooseleaf firstn -2 type host
>>
>> step emit
>>
>> }
>>
>> ------------------
>>
>>
>>
>> The replication size is set to 3.
>>
>>
>>
>> When for example ruleset 1 is used, how is the replication being done?
>> Does it store 2 replica’s in ams5-ssd and store 1 replica in ams6-ssd? Or
>> does it store 3 replicas in ams5-ssd and 3 replicas in ams6-ssd?
>>
>>
>>
>> Thanks!
>>
>>
>>
>> Sinan
>>
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>
>
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