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11.7. Expanding Volumes

Warning

If you follow this process with geo-replication configured, you run the risk of data loss when converting a volume. This race condition is tracked by Bug 1683893 and the workaround is available in the Red Hat Gluster Storage Release Notes.
Volumes can be expanded while the trusted storage pool is online and available. For example, you can add a brick to a distributed volume, which increases distribution and adds capacity to the Red Hat Gluster Storage volume. Similarly, you can add a group of bricks to a replicated or distributed replicated volume, which increases the capacity of the Red Hat Gluster Storage volume.
When expanding replicated or distributed replicated volumes, the number of bricks being added must be a multiple of the replica count. This also applies to arbitrated volumes. For example, to expand a distributed replicated volume with a replica count of 3, you need to add bricks in multiples of 3 (such as 6, 9, 12, etc.).
You can also convert a replica 2 volume into an arbitrated replica 3 volume by following the instructions in Section 5.8.5, “Converting to an arbitrated volume”.

Important

Converting an existing distribute volume to replicate or distribute-replicate volume is not supported.

Expanding a Volume

  1. From any server in the trusted storage pool, use the following command to probe the server on which you want to add a new brick: 
    # gluster peer probe HOSTNAME
    For example: 
    # gluster peer probe server5
Probe successful

# gluster peer probe server6
Probe successful
  2. Add the bricks using the following command: 
    # gluster volume add-brick VOLNAME NEW_BRICK
    For example: 
    # gluster volume add-brick test-volume server5:/rhgs/brick5/ server6:/rhgs/brick6/
Add Brick successful
  3. Check the volume information using the following command: 
    # gluster volume info
    The command output displays information similar to the following: 
    Volume Name: test-volume
Type: Distribute-Replicate
Status: Started
Number of Bricks: 6
Bricks:
Brick1: server1:/rhgs/brick1
Brick2: server2:/rhgs/brick2
Brick3: server3:/rhgs/brick3
Brick4: server4:/rhgs/brick4
Brick5: server5:/rhgs/brick5
Brick6: server6:/rhgs/brick6
  4. Rebalance the volume to ensure that files will be distributed to the new brick. Use the rebalance command as described in Section 11.11, “Rebalancing Volumes”.
    The add-brick command should be followed by a rebalance operation to ensure better utilization of the added bricks.

11.7.1. Expanding a Tiered Volume

You can add a group of bricks to a cold tier volume and to the hot tier volume to increase the capacity of the Red Hat Gluster Storage volume.

11.7.1.1. Expanding a Cold Tier Volume

Expanding a cold tier volume is same as a non-tiered volume. If you are reusing the brick, ensure to perform the steps listed in “Section 5.4.3, “ Reusing a Brick from a Deleted Volume ”” section.
  1. Detach the tier by performing the steps listed in Section 16.7, “Detaching a Tier from a Volume”
  2. From any server in the trusted storage pool, use the following command to probe the server on which you want to add a new brick : 
    # gluster peer probe HOSTNAME
    For example: 
    # gluster peer probe server5
Probe successful

# gluster peer probe server6
Probe successful
  3. Add the bricks using the following command: 
    # gluster volume add-brick VOLNAME NEW_BRICK
    For example: 
    # gluster volume add-brick test-volume server5:/rhgs/brick5/ server6:/rhgs/brick6/
  4. Rebalance the volume to ensure that files will be distributed to the new brick. Use the rebalance command as described in Section 11.11, “Rebalancing Volumes”.
    The add-brick command should be followed by a rebalance operation to ensure better utilization of the added bricks.
  5. Reattach the tier to the volume with both old and new (expanded) bricks:
    # gluster volume tier VOLNAME attach [replica COUNT] NEW-BRICK...

    Important

    When you reattach a tier, an internal process called fix-layout commences internally to prepare the hot tier for use. This process takes time and there will a delay in starting the tiering activities.
    If you are reusing the brick, be sure to clearly wipe the existing data before attaching it to the tiered volume.

11.7.1.2. Expanding a Hot Tier Volume

You can expand a hot tier volume by attaching and adding bricks for the hot tier.
  1. Detach the tier by performing the steps listed in Section 16.7, “Detaching a Tier from a Volume”
  2. Reattach the tier to the volume with both old and new (expanded) bricks:
    # gluster volume tier VOLNAME attach [replica COUNT] NEW-BRICK...
    For example, 
    # gluster volume tier test-volume attach replica 2 server1:/rhgs/tier5 server2:/rhgs/tier6 server1:/rhgs/tier7 server2:/rhgs/tier8

    Important

    When you reattach a tier, an internal process called fix-layout commences internally to prepare the hot tier for use. This process takes time and there will a delay in starting the tiering activities.
    If you are reusing the brick, be sure to clearly wipe the existing data before attaching it to the tiered volume.

11.7.2. Expanding a Dispersed or Distributed-dispersed Volume

Expansion of a dispersed or distributed-dispersed volume can be done by adding new bricks. The number of additional bricks should be in multiple of basic configuration of the volume. For example, if you have a volume with configuration (4+2 = 6), then you must only add 6 (4+2) or multiple of 6 bricks (such as 12, 18, 24 and so on).

Note

If you add bricks to a Dispersed volume, it will be converted to a Distributed-Dispersed volume, and the existing dispersed volume will be treated as dispersed subvolume.
  1. From any server in the trusted storage pool, use the following command to probe the server on which you want to add new bricks: 
    # gluster peer probe HOSTNAME
    For example: 
    # gluster peer probe server4
            Probe successful
            # gluster peer probe server5
            Probe successful
            # gluster peer probe server6
            Probe successful
  2. Add the bricks using the following command: 
    # gluster volume add-brick VOLNAME NEW_BRICK
    For example: 
    # gluster volume add-brick test-volume server4:/rhgs/brick7 server4:/rhgs/brick8 server5:/rhgs/brick9 server5:/rhgs/brick10 server6:/rhgs/brick11 server6:/rhgs/brick12
  3. (Optional) View the volume information after adding the bricks: 
    # gluster volume info VOLNAME
    For example: 
    # gluster volume info test-volume
Volume Name: test-volume
Type: Distributed-Disperse
Volume ID: 2be607f2-f961-4c4b-aa26-51dcb48b97df
Status: Started
Snapshot Count: 0
Number of Bricks: 2 x (4 + 2) = 12
Transport-type: tcp
Bricks:
Brick1: server1:/rhgs/brick1
Brick2: server1:/rhgs/brick2
Brick3: server2:/rhgs/brick3
Brick4: server2:/rhgs/brick4
Brick5: server3:/rhgs/brick5
Brick6: server3:/rhgs/brick6
Brick7: server4:/rhgs/brick7
Brick8: server4:/rhgs/brick8
Brick9: server5:/rhgs/brick9
Brick10: server5:/rhgs/brick10
Brick11: server6:/rhgs/brick11
Brick12: server6:/rhgs/brick12
Options Reconfigured:
transport.address-family: inet
performance.readdir-ahead: on
nfs.disable: on
  4. Rebalance the volume to ensure that the files will be distributed to the new brick. Use the rebalance command as described in Section 11.11, “Rebalancing Volumes”.
    The add-brick command should be followed by a rebalance operation to ensure better utilization of the added bricks.

11.7.3. Expanding Underlying Logical Volume

You can expand the size of a logical volume using the lvextend command.
Red Hat recommends following this process when you want to increase the storage capacity of replicated, arbitrated-replicated, or dispersed volumes, but not expanding distributed-replicated, arbitrated-distributed-replicated, or distributed-dispersed volumes.

Warning

It is recommended to involve the Red Hat Support team while performing this operation.
In the case of online logical volume extent, ensure the associated brick process is killed manually. It might occur certain operations are consuming data, or reading or writing a file on an associated brick. Proceeding with the extension before killing the brick process can have an adverse effect on performance. Identify the brick process ID and kill the same using the following command: 
# gluster volume status
# kill -9 brick-process-id
  1. Stop all volumes using the brick with the following command: 
    # gluster volume stop VOLNAME
  2. Check if new disk is visible using lsblk command: 
    # lsblk
  3. Create new physical volume using following command: 
    # pvcreate /dev/PHYSICAL_VOLUME_NAME
  4. Use the following command to verify if the physical volume is created: 
    # pvs
  5. Extend the existing volume group: 
    # vgextend VOLUME_GROUP_NAME /dev/PHYSICAL_VOLUME_NAME
  6. Use the following commands to check the size of volume group, and verify if it reflects the new addition: 
    # vgscan
  7. Ensure the volume group created has enough space to extend the logical volume: 
    vgdisplay VOLUME_GROUP_NAME
    Retrieve the file system name using the following command: 
    # df -h
  8. Extend the logical volume using the following command: 
    # lvextend -L+nG /dev/mapper/ LOGICAL_VOLUME_NAME-VOLUME_GROUP_NAME
    In case of thin pool, extend the pool using the following command: 
    # lvextend -L+nG VOLUME_GROUP_NAME/POOL_NAME
    In the above commands, n is the additional size in GB to be extended.
    Execute the #lvdisplay command to fetch the pool name.
    Use the following command to check if the logical volume is extended: 
    # lvdisplay VOLUME_GROUP_NAME
  9. Execute the following command to expand the filesystem to accommodate the extended logical volume: 
    # xfs_growfs /dev/VOLUME_GROUP_NAME/LOGICAL_VOLUME_NAME
  10. Remount the file system using the following command: 
    # mount -o remount /dev/VOLUME_GROUP_NAME/LOGICAL_VOLUME_NAME /bricks/path_to_brick
  11. Start all the volumes with force option: 
    # gluster volume start VOLNAME force