Add documentation for datastore role

roles/datastore/meta/argument_specs.yaml

@@ -0,0 +1,67 @@
+---
+argument_specs:
+  main:
+    description: >-
+      This role makes several assumptions about the local storage configuration of the server:
+
+      1. There is one block device on the server that will be used for data storage
+      2. That block device will be joined to a glusterfs volume
+      3. The block device is encrypted with LUKS
+
+      This role mostly serves to perform housekeeping tasks and validation of expected configs.
+      Automating disk configuration seems like a really good way to lose all my data, so I decided
+      to leave that to the much more reliable manual configuration for the time being.
+
+      To that end, here is a quick cheatsheet of commands that might be useful in setting up
+      storage device(s) for this role (replace `DEVICE` with the block device for storage):
+
+      ```bash
+      # Encrypt a block device, provide encryption key when prompted
+      cryptsetup luksFormat --type luks2 /dev/DEVICE
+
+      # Unlock encrypted block device and mount under a mapper
+      cryptsetup luksOpen /dev/DEVICE LABEL
+
+      # Lock an encrypted block device
+      cryptsetup luksClose LABEL
+
+      # Create and format a partition on the encrypted block device
+      mkfs.xfs /dev/mapper/LABEL -L LABEL
+
+      # Run from an existing server already in the gluster pool
+      # Add server to the gluster pool
+      gluster peer probe HOSTNAME
+
+      # To replace a brick from an already offline'd node, the old brick first needs to be force
+      # removed, replication reduced, and (if arbiter is enabled) any arbiter nodes removed
+      #
+      # Remove arbiter brick
+      gluster volume remove-brick VOLUME replica 2 HOSTNAME:/EXPORT force
+      # Remove dead data brick
+      gluster volume remove-brick VOLUME replica 1 HOSTNAME:/EXPORT force
+      # Remove dead node
+      gluster peer detach HOSTNAME
+      # Add new data brick
+      gluster volume add-brick VOLUME replica 2 HOSTNAME:/EXPORT start
+      #
+      # To re-add the arbiter you might need to clean up the `.glusterfs` directory and remove
+      # directory parametes from the old brick. These next commands need to be run on the host
+      # with the arbiter brick physically attached
+      #
+      rm -rf /EXPORT/.glusterfs
+      setfattr -x trusted.gfid /EXPORT
+      setfattr -x trusted.glusterfs.volume-id /EXPORT
+      # Re-add arbiter brick
+      gluster volume add-brick VOLUME replica 3 arbiter 1 HOSTNAME:/EXPORT
+      # Trigger a resync
+      gluster volume heal datastore
+
+      # General gluster debug info
+      gluster volume info VOLUME
+      gluster volume status VOLUME
+      ```
+    options:
+      skylab_datastore_device:
+        description: The block device under `/dev/` that should be configured as datastore storage
+        type: str
+        required: true