chmdisk

Use the chmdisk command to modify the name or IBM® Easy Tier® settings for a managed disk (MDisk).

Syntax

Parameters

-name new_name_arg

(Optional) Specifies the new name to be applied to the managed disk.

-tier tier0_flash | tier1_flash | tier_enterprise | tier_nearline | tier_scm

(Optional) Specifies the new tier of the MDisk. The values are:

tier0_flash: Specifies a tier0_flash hard disk drive or an external MDisk for the newly discovered or external volume.
tier1_flash: Specifies an tier1_flash (or flash drive) hard disk drive or an external MDisk for the newly discovered or external volume.
tier_enterprise: Specifies a tier_enterprise hard disk drive or an external MDisk for the newly discovered or external volume.
tier_nearline: Specifies a tier_nearline hard disk drive or an external MDisk for the newly discovered or external volume.
tier_scm: Specifies a tier_scm hard disk drive or an external MDisk for the newly discovered or external volume.

Note: Since Release 8.1.0, the tier of MDisks mapped from certain types of IBM System Storage® Enterprise Flash is fixed to tier0_flash, and cannot be changed.

-easytierload default | low | medium | high | very_high

(Optional) Specifies the Easy Tier load (amount) to place on a non-array MDisk within its tier.

If Easy Tier is either overusing or under-utilizing a particular MDisk, modify the easy_tier_load value to change the load size.

Note: Specifying default returns the performance capability to the value used by the system. Specify very_high only if the MDisk tier is ssd.

-encrypt yes | no

(Optional) Specifies whether the MDisk is encrypted by using its own encryption resources. The values are yes or no.

If you apply encryption to your system, you must identify the encrypted MDisks before you apply the encryption. If you specify chmdisk -encrypt, the setting is permanent in SAN Volume Controller no matter what Storwize® V7000 says.

mdisk_id | mdisk_name

(Required) Specifies the ID or name of the managed disk to modify.

Description

This command modifies the attributes of a managed disk.

Do not use the -encrypt parameter if one of the MDisk group's has an encryption key, parent pool, and child pools. Use chmdisk for existing self-encrypting MDisks before you start any migration. If an MDisk is self-encrypting, the encrypted property defaults to what is reported.

If you are upgrading your system and the back end of the system uses encrypted storage, you must indicate which MDisks are self-encrypting before you add MDisks to a storage pool. If those MDisks are part of a storage pool, the system assumes that the back-end is not self-encrypting (even if it might be).

If you create encrypted storage pools, the system encrypts locally before it sends data to the back-end. So, the back-end of the system could encrypt again and cannot compress data because the data is random and not compressible.

Note: You must upgrade the system first.

To use encryption on the system that already has encryption that is enabled on the back-end, upgrade the back-end of the system before you enable encryption on the system.

An invocation example

chmdisk -tier tier0_flash mdisk13

The resulting output:

No feedback

An invocation example

chmdisk -tier tier_nearline mdisk0

The resulting output:

MDisk Group, id [13], successfully created

An invocation example

chmdisk -easytierload high mdisk0

The resulting output:

MDisk Group, id [13], successfully created

An invocation example

chmdisk -name my_first_mdisk -encrypt yes 0

The resulting output:

MDisk Group, id [0], successfully changed