Chapter 2. Handling a disk failure

Procedure

1. Remove the block device from sysfs:

   Syntax

   echo 1 > /sys/block/BLOCK_DEVICE/device/delete

   Example

   [root@osd ~]# echo 1 > /sys/block/sdb/device/delete

   In the Ceph OSD log, on the OSD node, Ceph detected the failure and started the recovery process automatically.

   Example

   [root@osd ~]# tail -50 /var/log/ceph/ceph-osd.1.log
   2020-09-02 15:50:50.187067 7ff1ce9a8d80  1 bdev(0x563d263d4600 /var/lib/ceph/osd/ceph-2/block) close
   2020-09-02 15:50:50.440398 7ff1ce9a8d80 -1 osd.2 0 OSD:init: unable to mount object store
   2020-09-02 15:50:50.440416 7ff1ce9a8d80 -1 ^[[0;31m ** ERROR: osd init failed: (5) Input/output error^[[0m
   2020-09-02 15:51:10.633738 7f495c44bd80  0 set uid:gid to 167:167 (ceph:ceph)
   2020-09-02 15:51:10.633752 7f495c44bd80  0 ceph version 12.2.12-124.el7cp (e8948288b90d312c206301a9fcf80788fbc3b1f8) luminous (stable), process ceph-osd, pid 36209
   2020-09-02 15:51:10.634703 7f495c44bd80 -1 bluestore(/var/lib/ceph/osd/ceph-2/block) _read_bdev_label failed to read from /var/lib/ceph/osd/ceph-2/block: (5) Input/output error
   2020-09-02 15:51:10.635749 7f495c44bd80 -1 bluestore(/var/lib/ceph/osd/ceph-2/block) _read_bdev_label failed to read from /var/lib/ceph/osd/ceph-2/block: (5) Input/output error
   2020-09-02 15:51:10.636642 7f495c44bd80 -1 bluestore(/var/lib/ceph/osd/ceph-2/block) _read_bdev_label failed to read from /var/lib/ceph/osd/ceph-2/block: (5) Input/output error
   2020-09-02 15:51:10.637535 7f495c44bd80 -1 bluestore(/var/lib/ceph/osd/ceph-2/block) _read_bdev_label failed to read from /var/lib/ceph/osd/ceph-2/block: (5) Input/output error
   2020-09-02 15:51:10.641256 7f495c44bd80  0 pidfile_write: ignore empty --pid-file
   2020-09-02 15:51:10.669317 7f495c44bd80  0 load: jerasure load: lrc load: isa
   2020-09-02 15:51:10.669387 7f495c44bd80  1 bdev create path /var/lib/ceph/osd/ceph-2/block type kernel
   2020-09-02 15:51:10.669395 7f495c44bd80  1 bdev(0x55a423da9200 /var/lib/ceph/osd/ceph-2/block) open path /var/lib/ceph/osd/ceph-2/block
   2020-09-02 15:51:10.669611 7f495c44bd80  1 bdev(0x55a423da9200 /var/lib/ceph/osd/ceph-2/block) open size 500103643136 (0x7470800000, 466GiB) block_size 4096 (4KiB) rotational
   2020-09-02 15:51:10.670320 7f495c44bd80 -1 bluestore(/var/lib/ceph/osd/ceph-2/block) _read_bdev_label failed to read from /var/lib/ceph/osd/ceph-2/block: (5) Input/output error
   2020-09-02 15:51:10.670328 7f495c44bd80  1 bdev(0x55a423da9200 /var/lib/ceph/osd/ceph-2/block) close
   2020-09-02 15:51:10.924727 7f495c44bd80  1 bluestore(/var/lib/ceph/osd/ceph-2) _mount path /var/lib/ceph/osd/ceph-2
   2020-09-02 15:51:10.925582 7f495c44bd80 -1 bluestore(/var/lib/ceph/osd/ceph-2/block) _read_bdev_label failed to read from /var/lib/ceph/osd/ceph-2/block: (5) Input/output error
   2020-09-02 15:51:10.925628 7f495c44bd80  1 bdev create path /var/lib/ceph/osd/ceph-2/block type kernel
   2020-09-02 15:51:10.925630 7f495c44bd80  1 bdev(0x55a423da8600 /var/lib/ceph/osd/ceph-2/block) open path /var/lib/ceph/osd/ceph-2/block
   2020-09-02 15:51:10.925784 7f495c44bd80  1 bdev(0x55a423da8600 /var/lib/ceph/osd/ceph-2/block) open size 500103643136 (0x7470800000, 466GiB) block_size 4096 (4KiB) rotational
   2020-09-02 15:51:10.926549 7f495c44bd80 -1 bluestore(/var/lib/ceph/osd/ceph-2/block) _read_bdev_label failed to read from /var/lib/ceph/osd/ceph-2/block: (5) Input/output error

2. Looking at Ceph OSD disk tree, we also see the disk is offline.

   Example

   [root@osd ~]# ceph osd tree
   ID WEIGHT  TYPE NAME      UP/DOWN REWEIGHT PRIMARY-AFFINITY
   -1 0.28976 root default
   -2 0.09659     host ceph3
    1 0.09659         osd.1       down 1.00000          1.00000
   -3 0.09659     host ceph1
    2 0.09659         osd.2       up  1.00000          1.00000
   -4 0.09659     host ceph2
    0 0.09659         osd.0       up  1.00000          1.00000

Procedure

1. Check storage cluster health:

   [root@mon ~]# ceph health

2. Identify the OSD location in the CRUSH hierarchy:

   [root@mon ~]# ceph osd tree | grep -i down

3. On the OSD node, try to start the OSD:

   Syntax

   systemctl start ceph-osd@OSD_ID

   If the command indicates that the OSD is already running, there might be a heartbeat or networking issue. If you cannot restart the OSD, then the drive might have failed.

   Note

   If the OSD is down, then the OSD will eventually get marked out. This is normal behavior for Ceph Storage. When the OSD gets marked out, other OSDs with copies of the failed OSD’s data will begin backfilling to ensure that the required number of copies exist within the storage cluster. While the storage cluster is backfilling, the cluster will be in a degraded state.

4. For containerized deployments of Ceph, try to start the OSD container with the OSD_ID:

   Syntax

   systemctl start ceph-osd@OSD_ID

   If the command indicates that the OSD is already running, there might be a heartbeat or networking issue. If you cannot restart the OSD, then the drive might have failed.

   Note

   The drive associated with the OSD can be determined by Mapping a container OSD ID to a drive.

5. Check the failed OSD’s mount point:

   Note

   For containerized deployments of Ceph, if the OSD is down the container will be down and the OSD drive will be unmounted, so you cannot run df to check its mount point. Use another method to determine if the OSD drive has failed. For example, run smartctl on the drive from the container node.

   [root@osd ~]# df -h

   If you cannot restart the OSD, you can check the mount point. If the mount point no longer appears, then you can try remounting the OSD drive and restarting the OSD. If you cannot restore the mount point, then you might have a failed OSD drive.

   Using the smartctl utility cab help determine if the drive is healthy:

   Syntax

   yum install smartmontools
   smartctl -H /dev/BLOCK_DEVICE

   Example

   [root@osd ~]# smartctl -H /dev/sda

   If the drive has failed, you need to replace it.

6. Stop the OSD process:

   Syntax

   systemctl stop ceph-osd@OSD_ID

7. For containerized deployments of Ceph, stop the OSD container:

   Syntax

   systemctl stop ceph-osd@OSD_ID

8. Remove the OSD out of the storage cluster:

   Syntax

   ceph osd out OSD_ID

9. Ensure the failed OSD is backfilling:

   [root@osd ~]# ceph -w

10. Remove the OSD from the CRUSH Map:

    Syntax

    ceph osd crush remove osd.OSD_ID

    Note

    This step is only needed, if you are permanently removing the OSD and not redeploying it.

11. Remove the OSD’s authentication keys:

    Syntax

    ceph auth del osd.OSD_ID

12. Verify that the keys for the OSD are not listed:

    Example

    [root@osd ~]# ceph auth list

13. Remove the OSD from the storage cluster:

    Syntax

    ceph osd rm osd.OSD_ID

14. Unmount the failed drive path:

    Syntax

    umount /var/lib/ceph/osd/CLUSTER_NAME-OSD_ID

    Example

    [root@osd ~]# umount /var/lib/ceph/osd/ceph-0

    Note

    For containerized deployments of Ceph, if the OSD is down the container will be down and the OSD drive will be unmounted. In this case there is nothing to unmount and this step can be skipped.

15. Replace the physical drive. Refer to the hardware vendor’s documentation for the node. If the drive is hot swappable, simply replace the failed drive with a new drive. If the drive is NOT hot swappable and the node contains multiple OSDs, you MIGHT need to bring the node down to replace the physical drive. If you need to bring the node down temporarily, you might set the cluster to noout to prevent backfilling:

    Example

    [root@osd ~]# ceph osd set noout

    Once you replace the drive and you bring the node and its OSDs back online, remove the noout setting:

    Example

    [root@osd ~]# ceph osd unset noout

    Allow the new drive to appear under the /dev/ directory and make a note of the drive path before proceeding further.

16. Find the OSD drive and format the disk.

17. Recreate the OSD:

    1. Using Ceph Ansible.
    2. Using the command-line interface.

18. Check the CRUSH hierarchy to ensure it is accurate:

    Example

    [root@osd ~]# ceph osd tree

    If you are not satisfied with the location of the OSD in the CRUSH hierarchy, you can move it with the move command:

    Syntax

    ceph osd crush move BUCKET_TO_MOVE BUCKET_TYPE=PARENT_BUCKET

19. Verify the OSD is online.

Procedure

1. Destroy the OSD:

   Syntax

   ceph osd destroy OSD_ID --yes-i-really-mean-it

   Example

   [root@osd ~]# ceph osd destroy 1 --yes-i-really-mean-it

2. Optionally, if the replacement disk was used previously, then you need to zap the disk:

   Syntax

   ceph-volume lvm zap DEVICE

   Example

   [root@osd ~]# ceph-volume lvm zap /dev/sdb

   Note

   You can find the DEVICE by comparing output from various commands, such as ceph osd tree, ceph osd metadata, and df.

3. Create the new OSD with the existing OSD ID:

   Syntax

   ceph-volume lvm create --osd-id OSD_ID --data DEVICE

   Example

   [root@mon ~]# ceph-volume lvm create --osd-id 1 --data /dev/sdb