Thank you very much for the thorough explanation. What you described was one of
the ways I was interpreting this.
Now, out of curiosity, if I did:
rule replicated_rack {
ruleset 0
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
}
Would that choose the 2 racks, and then 2 osds from each host, making sure that
in a 3x replication scenario, I would ensure that all 3 reps would be on
different servers as well? Just want to make sure I'm following the logic
correctly before I pull any triggers.
Cheers,
-
Stephen Mercier | Sr. Systems Architect
Attainia Capital Planning Solutions (ACPS)
O: (650)241-0567, 727 | TF: (866)288-2464, 727
stephen.merc...@attainia.com | www.attainia.com
On May 12, 2016, at 2:36 PM, Stephen Mercier wrote:
> I'm trying to setup a crush rule, and I was hoping you guys could clarify
> something for me.
>
> I have 4 storage nodes across 2 cabinets. (2x2)
>
> I have the crush hierarchy setup to reflect this layout (as follows):
>
> rack cabinet2 {
> id -3 # do not change unnecessarily
> # weight xxxx
> alg straw
> hash 0 # rjenkins1
> item cephstore04 weight xxxx
> item cephstore02 weight xxxx
> }
> rack cabinet1 {
> id -3 # do not change unnecessarily
> # weight xxxx
> alg straw
> hash 0 # rjenkins1
> item cephstore03 weight xxxx
> item cephstore01 weight xxxx
> }
> root default {
> id -1 # do not change unnecessarily
> # weight xxxx
> alg straw
> hash 0 # rjenkins1
> item cabinet2 weight xxxx
> item cabinet1 weight xxxx
> }
>
> The default ruleset is as follows: (Big surprise!!)
>
> rule replicated_ruleset {
> ruleset 0
> type replicated
> min_size 1
> max_size 10
> step take default
> step choose firstn 0 type osd
> step emit
> }
>
> If I want this to ensure that there is at least 1 copy of the data in each
> cabinet, would I just change it to:
>
> rule replicated_ruleset {
> ruleset 0
> type replicated
> min_size 1
> max_size 10
> step take default
> step choose firstn 0 type rack
> step emit
> }
>
> Or should it be:
>
> rule replicated_ruleset {
> ruleset 0
> type replicated
> min_size 1
> max_size 10
> step take default
> step chooseleaf firstn 0 type rack
> step emit
> }
>
> Or is there something more complicated I should be doing? I took a look at
> https://www.mail-archive.com/ceph-users@lists.ceph.com/msg19140.html and it
> sounds like this is what I want, but I've also see examples like the
> following:
>
> rule replicated_ruleset {
> ruleset 0
> type replicated
> min_size 1
> max_size 10
> step take default
> step choose firstn 2 type rack
> step chooseleaf firstn 0 type osd
> step emit
> }
>
> As you might have noticed, I'm a little confused, so any assistance is
> greatly appreciated. And just to clarify once more, I want to make sure that
> it stores at least one copy in each rack. Advice on getting more granular is
> welcome as well however, as I there are pools with both 2x and 3x replication
> setup.
>
> Cheers,
> -
> Stephen Mercier | Sr. Systems Architect
> Attainia Capital Planning Solutions (ACPS)
> O: (650)241-0567, 727 | TF: (866)288-2464, 727
> stephen.merc...@attainia.com | www.attainia.com
>
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