Local Pool Module

The localpool module can automatically create RADOS pools that are localized to a subset of the overall cluster. For example, by default, it creates a pool for each distinct rack in the cluster. This can be useful for deployments where it is desirable to distribute some data locally and other data globally across the cluster. One use case is measuring performance and testing behavior of specific drive, NIC, or chassis models in isolation.

Enabling

To enable the localpool module, run the following command:

ceph mgr module enable localpool

Configuring

The localpool module understands the following options:

subtree

which CRUSH subtree type the module should create a pool for.

type:

str

default:

rack

failure_domain

what failure domain we should separate data replicas across.

type:

str

default:

host

pg_num

default pg_num for any created local pool

type:

int

default:

128

num_rep

default replica count for any created local pool

type:

int

default:

3

min_size

value to set min_size to (unchanged from Ceph’s default if this option is not set)

type:

int

prefix

name prefix for any created local pool

type:

str

default:

<empty string>

The default is by-$subtreetype-.

These options are set via the config-key interface. For example, to change the replication level to 2x with 64 PGs, run the following two commands:

ceph config set mgr mgr/localpool/num_rep 2
ceph config set mgr mgr/localpool/pg_num 64

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