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Replace a failed Ceph OSD with a metadata device as a logical volume path¶

Warning

This procedure is valid for MOSK clusters that use the deprecated KaaSCephCluster custom resource (CR) instead of the MiraCeph CR that is available since MOSK 25.2 as a new Ceph configuration entrypoint. For the equivalent procedure with the MiraCeph CR, refer to the following section:

Replace a failed Ceph OSD with a metadata device as a logical volume path

You can apply the below procedure in the following cases:

A Ceph OSD failed without data or metadata device outage. In this case, first remove a failed Ceph OSD and clean up all corresponding disks and partitions. Then add a new Ceph OSD to the same data and metadata paths.
A Ceph OSD failed with data or metadata device outage. In this case, you also first remove a failed Ceph OSD and clean up all corresponding disks and partitions. Then add a new Ceph OSD to a newly replaced data device with the same metadata path.

Note

The below procedure also applies to manually created metadata partitions.

Remove a failed Ceph OSD by ID with a defined metadata device¶

Identify the ID of Ceph OSD related to a failed device. For example, use the Ceph CLI in the rook-ceph-tools Pod:

ceph osd metadata

Example of system response:

{
    "id": 0,
    ...
    "bluestore_bdev_devices": "vdc",
    ...
    "devices": "vdc",
    ...
    "hostname": "kaas-node-6c5e76f9-c2d2-4b1a-b047-3c299913a4bf",
    ...
    "pod_name": "rook-ceph-osd-0-7b8d4d58db-f6czn",
    ...
},
{
    "id": 1,
    ...
    "bluefs_db_devices": "vdf",
    ...
    "bluestore_bdev_devices": "vde",
    ...
    "devices": "vde,vdf",
    ...
    "hostname": "kaas-node-6c5e76f9-c2d2-4b1a-b047-3c299913a4bf",
    ...
    "pod_name": "rook-ceph-osd-1-78fbc47dc5-px9n2",
    ...
},
...

Open the KaasCephCluster custom resource (CR) for editing:
```
kubectl edit kaascephcluster -n <moskClusterProjectName>
```
Substitute <moskClusterProjectName> with the corresponding value.

In the nodes section:

Find and capture the metadataDevice path to reuse it during re-creation of the Ceph OSD.
Remove the required device:

Example configuration snippet:

spec:
  cephClusterSpec:
    nodes:
      <machineName>:
        storageDevices:
        - name: <deviceName>  # remove the entire item from the storageDevices list
          # fullPath: <deviceByPath> if device is specified using by-path instead of name
          config:
            deviceClass: hdd
            metadataDevice: /dev/bluedb/meta_1

In the example above, <machineName> is the name of machine that relates to the node on which the device <deviceName> or <deviceByPath> must be replaced.

Create a KaaSCephOperationRequest CR template and save it as replace-failed-osd-<machineName>-<osdID>-request.yaml:
```
apiVersion: kaas.mirantis.com/v1alpha1
kind: KaaSCephOperationRequest
metadata:
  name: replace-failed-osd-<machineName>-<deviceName>
  namespace: <moskClusterProjectName>
spec:
  osdRemove:
    nodes:
      <machineName>:
        cleanupByOsdId:
        - <osdID>
  kaasCephCluster:
    name: <kaasCephClusterName>
    namespace: <moskClusterProjectName>
```
Substitute the following parameters:
- <machineName> and <deviceName> with the machine and device names from the previous step
- <moskClusterProjectName> with the cluster project name
- <osdID> with the ID of the affected Ceph OSD
- <kaasCephClusterName> with the KaaSCephCluster resource name
- <moskClusterProjectName> with the project name of the related MOSK cluster

Apply the template to the cluster:

kubectl apply -f replace-failed-osd-<machineName>-<osdID>-request.yaml

Verify that the corresponding request has been created:

kubectl get kaascephoperationrequest -n <moskClusterProjectName>

Verify that the status section of KaaSCephOperationRequest contains the removeInfo section:

kubectl -n <moskClusterProjectName> get kaascephoperationrequest replace-failed-osd-<machineName>-<osdID> -o yaml

Example of system response:

childNodesMapping:
  <nodeName>: <machineName>
removeInfo:
  cleanUpMap:
    <nodeName>:
      osdMapping:
        "<osdID>":
          deviceMapping:
            <dataDevice>:
              deviceClass: hdd
              devicePath: <dataDeviceByPath>
              devicePurpose: block
              usedPartition: /dev/ceph-d2d3a759-2c22-4304-b890-a2d87e056bd4/osd-block-ef516477-d2da-492f-8169-a3ebfc3417e2
              zapDisk: true
            <metadataDevice>:
              deviceClass: hdd
              devicePath: <metadataDeviceByPath>
              devicePurpose: db
              usedPartition: /dev/bluedb/meta_1
          uuid: ef516477-d2da-492f-8169-a3ebfc3417e2

Definition of values in angle brackets:

<machineName> - name of the machine on which the device is being replaced, for example, worker-1
<nodeName> - underlying node name of the machine, for example, kaas-node-5a74b669-7e53-4535-aabd-5b509ec844af
<osdId> - Ceph OSD ID for the device being replaced, for example, 1
<dataDeviceByPath> - by-path of the device placed on the node, for example, /dev/disk/by-path/pci-0000:00:1t.9
<dataDevice> - name of the device placed on the node, for example, /dev/vde
<metadataDevice> - metadata name of the device placed on the node, for example, /dev/vdf
<metadataDeviceByPath> - metadata by-path of the device placed on the node, for example, /dev/disk/by-path/pci-0000:00:12.0

Note

The partitions that are manually created or configured using the BareMetalHostProfile object can be removed only manually, or during a complete metadata disk removal, or during the Machine object removal or re-provisioning.

Verify that the cleanUpMap section matches the required removal and wait for the ApproveWaiting phase to appear in status:

kubectl -n <moskClusterProjectName> get kaascephoperationrequest replace-failed-osd-<machineName>-<osdID> -o yaml

Example of system response:

status:
  phase: ApproveWaiting

In the KaaSCephOperationRequest CR, set the approve flag to true:

kubectl -n <moskClusterProjectName> edit kaascephoperationrequest replace-failed-osd-<machineName>-<osdID>

Configuration snippet:

spec:
  osdRemove:
    approve: true

Review the following status fields of the Ceph LCM CR request processing:
- status.phase - current state of request processing
- status.messages - description of the current phase
- status.conditions - full history of request processing before the current phase
- status.removeInfo.issues and status.removeInfo.warnings - error and warning messages occurred during request processing, if any

Verify that the KaaSCephOperationRequest has been completed. For example:

status:
  phase: Completed # or CompletedWithWarnings if there are non-critical issues

Re-create a Ceph OSD with the same metadata partition¶

Note

You can spawn Ceph OSD on a raw device, but it must be clean and without any data or partitions. If you want to add a device that was in use, also ensure it is raw and clean. To clean up all data and partitions from a device, refer to official Rook documentation.

If you want to add a Ceph OSD on top of a raw device that already exists on a node or is hot-plugged, add the required device using the following guidelines:
- You can add a raw device to a node during node deployment.
- If a node supports adding devices without node reboot, you can hot plug a raw device to a node.
- If a node does not support adding devices without node reboot, you can hot plug a raw device during node shutdown. In this case, complete the following steps:
  1. Enable maintenance mode on the MOSK cluster.
  2. Turn off the required node.
  3. Attach the required raw device to the node.
  4. Turn on the required node.
  5. Disable maintenance mode on the MOSK cluster.
Open the KaasCephCluster CR for editing:
```
kubectl edit kaascephcluster -n <moskClusterProjectName>
```
Substitute <moskClusterProjectName> with the corresponding value.

In the nodes section, add the replaced device with the same metadataDevice path as on the removed Ceph OSD. For example:

spec:
  cephClusterSpec:
    nodes:
      <machineName>:
        storageDevices:
        - name: <deviceByID> # Recommended. Add a new device by ID, for example, /dev/disk/by-id/...
          #fullPath: <deviceByPath> # Add a new device by path, for example, /dev/disk/by-path/...
          config:
            deviceClass: hdd
            metadataDevice: /dev/bluedb/meta_1 # Must match the value of the previously removed OSD

Substitute <machineName> with the machine name of the node where the new device <deviceByID> or <deviceByPath> must be added.

Wait for the replaced disk to apply to the Ceph cluster as a new Ceph OSD.

You can monitor the application state using either the status section of the KaaSCephCluster CR or in the rook-ceph-tools Pod:
```
kubectl -n rook-ceph exec -it deploy/rook-ceph-tools -- ceph -s
```