<a id="howto-cluster-storage"></a>

# How to configure storage for a cluster

All members of a cluster must have identical storage pools.
The only configuration keys that may differ between pools on different members are [`source`](https://canonical.com/lxd/docs/latest/reference/storage_drivers/index.html.md#storage-drivers), [`size`](https://canonical.com/lxd/docs/latest/reference/storage_drivers/index.html.md#storage-drivers), [`zfs.pool_name`](https://canonical.com/lxd/docs/latest/reference/storage_zfs/index.html.md#storage-zfs-pool-conf:zfs.pool_name), [`lvm.thinpool_name`](https://canonical.com/lxd/docs/latest/reference/storage_lvm/index.html.md#storage-lvm-pool-conf:lvm.thinpool_name) and [`lvm.vg_name`](https://canonical.com/lxd/docs/latest/reference/storage_lvm/index.html.md#storage-lvm-pool-conf:lvm.vg_name).
See [Member configuration](https://canonical.com/lxd/docs/latest/explanation/clusters/index.html.md#clustering-member-config) for more information.

LXD creates a default `local` storage pool for each cluster member during initialization.

Creating additional storage pools is a two-step process:

1. Define and configure the new storage pool across all cluster members.
   For example, for a cluster that has three members:
   ```none
   lxc storage create --target server1 data zfs source=/dev/vdb1
   lxc storage create --target server2 data zfs source=/dev/vdc1
   lxc storage create --target server3 data zfs source=/dev/vdb1 size=10GiB
   ```

   #### NOTE
   You can pass only the member-specific configuration keys `source`, `size`, `zfs.pool_name`, `lvm.thinpool_name` and `lvm.vg_name`.
   Passing other configuration keys results in an error.

   These commands define the storage pool, but they don’t create it.
   If you run [`lxc storage list`](https://canonical.com/lxd/docs/latest/reference/manpages/lxc/storage/list/index.html.md#lxc-storage-list-md), you can see that the pool is marked as “pending”.
2. Run the following command to instantiate the storage pool on all cluster members:
   ```none
   lxc storage create data zfs
   ```

   #### NOTE
   You can add configuration keys that are not member-specific to this command.

   If you missed a cluster member when defining the storage pool, or if a cluster member is down, you get an error.

Also see [Create a storage pool in a cluster](https://canonical.com/lxd/docs/latest/howto/storage_pools/index.html.md#howto-storage-pools-create-cluster).

<a id="howto-cluster-storage-view"></a>

## View member-specific pool configuration

Running [`lxc storage show <pool_name>`](https://canonical.com/lxd/docs/latest/reference/manpages/lxc/storage/show/index.html.md#lxc-storage-show-md) shows the cluster-wide configuration of the storage pool.

To view the member-specific configuration, use the `--target` flag.
For example:

```none
lxc storage show data --target server2
```

## Create storage volumes

For most storage drivers (all except for Ceph-based storage drivers), storage volumes are not replicated across the cluster and exist only on the member for which they were created.
Run [`lxc storage volume list <pool_name>`](https://canonical.com/lxd/docs/latest/reference/manpages/lxc/storage/volume/list/index.html.md#lxc-storage-volume-list-md) to see on which member a certain volume is located.

When creating a storage volume, use the `--target` flag to create a storage volume on a specific cluster member.
Without the flag, the volume is created on the cluster member on which you run the command.
For example, to create a volume on the current cluster member `server1`:

```none
lxc storage volume create local vol1
```

To create a volume with the same name on another cluster member:

```none
lxc storage volume create local vol1 --target server2
```

Different volumes can have the same name as long as they live on different cluster members.
Typical examples for this are image volumes.

You can manage storage volumes in a cluster in the same way as you do in non-clustered deployments, except that you must pass the `--target` flag to your commands if more than one cluster member has a volume with the given name.
For example, to show information about the storage volumes:

```none
lxc storage volume show local vol1 --target server1
lxc storage volume show local vol1 --target server2
```