Shrinking a Cluster

This page describes the procedures involved in the shrinking of a cluster, which may be required when it is necessary to reallocate cluster hardware.

Options for Shrinking a Cluster

Cluster shrinking can involve either the removal of some of the assigned SSDs or the removal of hosts from the system. The following operations are available:

  1. Listing all the drives and their states, in order to receive a view of currently-allocated resources and their status.

  2. Deactivating drives, which can be used for either removing a subset of the SSDs allocated, or as the first step before removing a host.

  3. Deactivating hosts, which can be used after its drives have been deactivated, in preparation for the removal of the host.

  4. Removing hosts in order to complete the cluster shrinking.

Listing Drives and Their States

Command: weka cluster drive

Using this command displays a list of all the drives in the cluster and their status.

Deactivating a Drive

Command: weka cluster drive deactivate

Running the deactivation command will redistribute the stored data on the remaining drives and can be performed on multiple drives.

Note: After running this command, the deactivated drives will still appear in the list.

Note: It is not possible to deactivate a drive if it will lead to an unstable state, i.e., if the system capacity after drive deactivation is insufficient for the currently provisioned filesystems SSD capacity.

Drive deactivation starts an asynchronous process known as phasing out, which is a gradual redistribution of the data between the remaining drives in the system. On completion, the phased-out drive is in an inactive state i.e., not in use by the WekaIO system, but still appearing in the list of drives.

Note: Running the weka cluster drive command will display whether the redistribution is still being performed.

To deactivate a drive, run the following command line:

weka cluster drive deactivate <drive-uuids>…

Parameters in Command Line

Name

Type

Value

Limitations

Mandatory

Default

uuids

Comma-separated strings

Comma-separated drive identifiers

.

Yes

Deactivating an Entire Host

Command: weka cluster host deactivate

This command is used as the first step when seeking to shrink a cluster. Running it is mandatory to deactivate the relevant host drives prior to removal of the host, thereby terminating the IO participation of the host in the cluster. All the host drives must have been previously deactivated.

To deactivate an entire host, run the following command line:

weka cluster host deactivate <host-ids>…

Parameters in Command Line

Name

Type

Value

Limitations

Mandatory

Default

host-ids

Comma-separated strings

Comma-separated host identifiers

.

Yes

Removing a Host

Command: weka cluster host remove

Running this command will eliminate the host from the cluster, i.e., the host will switch to the stem mode after the removal, at which point it can be reallocated either to another cluster or another purpose.

To remove the host from the cluster, run the following command:

weka cluster host remove <host-id>…

Parameters in Command Line

Name

Type

Value

Limitations

Mandatory

Default

host-id

Comma-separated strings

Comma-separated host identifiers

.

Yes