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.
Thank you for your advice.
Edward
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