[rdo-users] Creating CRUSH placement rules with TripleO

[John Fulton]

On Saturday, October 13, 2018, Cody <codeology.lab at gmail.com> wrote:

> Hi everyone,
>
> Is it possible to define CRUSH placement rules and apply to different
> pools while using TripleO to deploy an overcloud with Ceph
> integration?
>
> I wish to set the "vms" pool to use SSDs and "volumes" pool to use
> HDDs. On a pre-existing Ceph cluster, I can define CRUSH placement
> rules using device-class and apply the corresponding rules when create
> pools. But, I don't know how to do so with TripleO.
>
> Could someone shed light on this?
>

CRUSH rules may be passed to specific nodes. You may identify specific
nodes in TripleO by using node-specific overrides as per:

https://docs.openstack.org/tripleo-docs/latest/install/advanced_deployment/node_specific_hieradata.html

In the documentation above a specific devices list is passed to a specific
node. However, you may pass other properties to the specific node including
the osd_crush_location. For example:

{"32C2BC31-F6BB-49AA-971A-377EFDFDB111": {"osd_crush_location": {"root":
"standard_root", "rack": "rack1_std", "host": "lab-ceph01"}},

TripleO then will map the node's UUID to the IP used in the ceph-ansible
inventory and pass node specific variable overrides.

You'll also want to use CephAnsibleExtraConfig to override specific
ceph-ansible variables for all nodes, e.g.

  CephAnsibleExtraConfig:
    create_crush_tree: true

More info at
https://docs.openstack.org/tripleo-docs/latest/install/advanced_deployment/ceph_config.html

Overall, if you know how to make ceph-ansible do what you need it to do,
then TripleO can pass the variables to ceph-ansible to achieve it.

  John


>
> Best regards,
> Cody
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