diff --git a/docs/guides/other-guides/testbed.mdx b/docs/guides/other-guides/testbed.mdx
index 08f67d256d..ed180f44b9 100644
--- a/docs/guides/other-guides/testbed.mdx
+++ b/docs/guides/other-guides/testbed.mdx
@@ -595,6 +595,63 @@ of the other cloud is changed accordingly.
 | `/opt/configuration/scripts/upgrade/320-openstack-services-baremetal.sh`  |             |
 | `/opt/configuration/scripts/upgrade/330-openstack-services-additional.sh` |             |
 
+### Add new OSD in Ceph
+
+In the testbed, three volumes per node are provided for use by Ceph by default. Two of
+these devices are used as OSDs during the initial deployment. The third device is intended
+for testing the addition of a further OSD to the Ceph cluster.
+
+1. Add `sdd` to `ceph_osd_devices` in `/opt/configuration/inventory/host_vars/testbed-node-0.testbed.osism.xyz/ceph-lvm-configuration.yml`.
+   The following content is an example, the IDs look different everywhere. Do not copy 1:1
+   but only add `sdd` to the file.
+
+```yaml
+---
+#
+# This is Ceph LVM configuration for testbed-node-0.testbed.osism.xyz
+# generated by ceph-configure-lvm-volumes playbook.
+#
+ceph_osd_devices:
+  sdb:
+    osd_lvm_uuid: 95a9a2e0-b23f-55b2-a04f-e02ddfc0e82a
+  sdc:
+    osd_lvm_uuid: 29899765-42bf-557b-ae9c-5c7c984b2243
+  sdd:
+lvm_volumes:
+- data: osd-block-95a9a2e0-b23f-55b2-a04f-e02ddfc0e82a
+  data_vg: ceph-95a9a2e0-b23f-55b2-a04f-e02ddfc0e82a
+- data: osd-block-29899765-42bf-557b-ae9c-5c7c984b2243
+  data_vg: ceph-29899765-42bf-557b-ae9c-5c7c984b2243
+```
+
+2. Run `osism apply ceph-configure-lvm-volumes -l testbed-node-0.testbed.osism.xyz`
+
+3. Run `cp /tmp/testbed-node-0.testbed.osism.xyz-ceph-lvm-configuration.yml /opt/configuration/inventory/host_vars/testbed-node-0.testbed.osism.xyz/ceph-lvm-configuration.yml`.
+
+4. Run `osism reconciler sync`
+
+5. Run `osism apply ceph-create-lvm-devices -l testbed-node-0.testbed.osism.xyz`
+
+6. Run `osism apply ceph-osds -l testbed-node-0.testbed.osism.xyz -e ceph_handler_osds_restart=false`
+
+7. Check the OSD tree
+
+   ```
+   $ ceph osd tree
+   ID  CLASS  WEIGHT   TYPE NAME                STATUS  REWEIGHT  PRI-AFF
+   -1         0.13640  root default
+   -3         0.05846      host testbed-node-0
+    2    hdd  0.01949          osd.2                up   1.00000  1.00000
+    4    hdd  0.01949          osd.4                up   1.00000  1.00000
+    6    hdd  0.01949          osd.6                up   1.00000  1.00000
+   -5         0.03897      host testbed-node-1
+    0    hdd  0.01949          osd.0                up   1.00000  1.00000
+    5    hdd  0.01949          osd.5                up   1.00000  1.00000
+   -7         0.03897      host testbed-node-2
+    1    hdd  0.01949          osd.1                up   1.00000  1.00000
+    3    hdd  0.01949          osd.3                up   1.00000  1.00000
+   ```
+
 ### Ceph via Rook (technical preview)
 
 Please have a look at [Deploy Guide - Services - Rook](../deploy-guide/services/rook.md) and [Configuration Guide - Rook](../configuration-guide/rook.md) for details on how to configure Rook.