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/[email protected]/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
[email protected] | www.attainia.com
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