On 01/15/2013 11:34 AM, Gandalf Corvotempesta wrote:
2013/1/15 Wido den Hollander <wido@xxxxxxxxx>:
Yes, no problem at all! That's where the crushmap is for. This way you can
tell Ceph exactly how to distribute your data.
Cool.
If I understood properly, I have to configure ceph with OSD in a
standard way and then
map these osd into a custom crushmap like this:
host node1 {
id -1
alg straw
hash 0
item osd.0 weight 1.00
item osd.1 weight 1.00
}
host node2 {
id -2
alg straw
hash 0
item osd.2 weight 1.00
item osd.3 weight 1.00
}
rack rack1 {
id -3
alg straw
hash 0
item node1 weight 2.00
}
rack rack2 {
id -4
alg straw
hash 0
item node2 weight 2.00
}
This one should allow me to have 4 OSDs, 2 servers and 2 racks. Each
rack with one server with 2 OSDs
Data will be automatically striped across both rack, right?
Almost! A couple of things:
You don't have to sum the weight of a node in the rack, crush will sum
the nodes automatically. If all nodes are equal there is no need to do so.
You need to add this as well:
root default {
id -1
alg straw
hash 0
item rack1
item rack2
}
rule data {
ruleset 0
type replicated
min_size 1
max_size 10
step take default
step chooseleaf firstn 0 type rack
step emit
}
You should know that you can never set replication higher then 2 with
this setting since it always tries to pick a rack and you only have two.
Wido
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