[ceph-users] Crush Map and SSD Pools

[Lindsay Mathieson]

I looked at the section for setting up different pools with different OSD's 
(e.g SSD Pool):

  
http://ceph.com/docs/master/rados/operations/crush-map/#placing-different-pools-on-different-osds

And it seems to make the assumption that the ssd's and platters all live on 
separate hosts.

Not the case at all for my setup and I imagine for most people I have ssd's 
mixed with
platters on the same hosts.

In that case should one have the root buckets referencing buckets not based on 
hosts, e.g,
something like this:


# devices
# Platters
device 0 osd.0
device 1 osd.1

# SSD
device 2 osd.2
device 3 osd.3

host vnb {
        id -2           # do not change unnecessarily
        # weight 1.000
        alg straw
        hash 0  # rjenkins1
        item osd.0 weight 1.000
        item osd.2 weight 1.000
}
host vng {
        id -3           # do not change unnecessarily
        # weight 1.000
        alg straw
        hash 0  # rjenkins1
        item osd.1 weight 1.000
        item osd.3 weight 1.000
}

row disk-platter {
        alg straw
        hash 0  # rjenkins1
        item osd.0 weight 1.000
        item osd.1 weight 1.000
}

row disk-ssd {
        alg straw
        hash 0  # rjenkins1
        item osd.2 weight 1.000
        item osd.3 weight 1.000
}


root default {
        id -1           # do not change unnecessarily
        # weight 2.000
        alg straw
        hash 0  # rjenkins1
        item disk-platter weight 2.000
}

root ssd {
              id -4
              alg straw
              hash 0
              item disk-ssd weight 2.000
      }

# rules
rule replicated_ruleset {
        ruleset 0
        type replicated
        min_size 1
        max_size 10
        step take default
        step chooseleaf firstn 0 type host
        step emit
}

rule ssd {
              ruleset 1
              type replicated
              min_size 0
              max_size 4
              step take ssd
              step chooseleaf firstn 0 type host
              step emit
      }


--
Lindsay

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