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:
Listing all the drives and their states, in order to receive a view of currently-allocated resources and their status.
Deactivating drives as the first step before removing a host.
Removing (a subset of) SSD drives allocated for the cluster.
Deactivating hosts, which can be used after deactivating drives in preparation for the removal of the host.
Removing hosts in order to complete the cluster shrinking.
Listing Drives and Their States
Command: weka cluster drive
Use this command to display a list of all the drives in the cluster and their status.
Deactivating a Drive
Command: weka cluster drive deactivate
Running this 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 SSD capacity of currently-provisioned filesystems.
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 Weka 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:
weka cluster drive deactivate <uuids>
Parameters in Command Line
Name
Type
Value
Limitations
Mandatory
Default
uuids
Comma-separated strings
Comma-separated drive identifiers
Yes
Removing a Drive
Command: weka cluster drive remove
This command is used to completely remove a drive from the cluster. After removal, the drive will not be recoverable.
To remove a drive, run the following command:
weka cluster drive remove <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 this command will automatically deactivate all the host's drives.
To deactivate an entire host, run the following command:
weka cluster host deactivate <host-ids> [--allow-unavailable]
Parameters in Command Line
Name
Type
Value
Limitations
Mandatory
Default
host-ids
Space-separated integers
Space-separated host identifiers
Yes
allow-unavailable
Boolean
Allow deactivation of an unavailable host
If the host returns, it will join the cluster in an active state
No
No
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 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
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