Is it possible to create replication rule that uses two osd classes and uses them in equal manner?

[miro-zamiro]

Hi!
I'm a sysadmin hobbist. I have a cluster of three ceph nodes with 10 osds. As I consider it as my hobby I have limited resources. Is it possible to set a replication rule with two classes (ssd and hdd) that would treat these classes equally?
I know about this option:
´´´
rule mixed_replicated_rule {
id 11
type replicated
step take default class ssd
step chooseleaf firstn 1 type host
step emit
step take default class hdd
step chooseleaf firstn 0 type host
step emit
}
´´´
But it always defaults to ssd class in the first step.
Is it possible to accomplish?
Best,
Miro

 

[fba]

Hi,
no need to choose a device class in the rule, if you dont want to.
This is taken from Ceph documentation: https://docs.ceph.com/en/latest/rad...ting-from-a-legacy-ssd-rule-to-device-classes

rule mixed_replicated_rule {
    id 11
    type replicated
    step take default
    step chooseleaf firstn 0 type host
    step emit
}

 

[Nemesiz]

I suggest you take a look at these links

https://www.osris.org/article/2019/03/01/ceph-osd-site-affinity
https://ceph.io/en/news/blog/2015/crushmap-example-of-a-hierarchical-cluster-map/