mkmdiskgrp

Use the mkmdiskgrp command to create a new storage pool.

Syntax

Read syntax diagramSkip visual syntax diagram mkmdiskgrp -namepool_name-mdiskmdisk_id_listmdisk_name_list-tiertier0_flashtier1_flashtier_enterprisetier_nearlinetier_scm-extextent_size-parentmdiskgrpmdiskgrp_idmdiskgrp_name-sizemdiskgrp_size-noquota-safeguarded-warningdisk_sizedisk_size_percentage%-unitbkbmbgbtbpb-easytierautoonoffmeasure-ownerowner_type-encryptyesno-datareductionyesno-provisioningpolicyprovisioning_policy_id | provisioning_policy_name-etfcmoverallocationmaxpercentage | off-vdiskprotectionenabledyesnoreplicationpoollinkuidreplication_pool_link_uid

Parameters

-name pool_name
(Optional) Specifies a name to assign to the new pool.
-mdisk mdisk_id_list | mdisk_name_list
(Optional) Specifies a colon-separated list of managed disk IDs or names to add to the storage pool. You can create an empty storage pool by not specifying the -mdisk parameter.
-tier tier0_flash | tier1_flash | tier_enterprise | tier_nearline | tier_scm
(Optional) Specifies the tier of the MDisk or MDisks being added.
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.

If you do not specify a tier, the current tier value of the MDisk is retained. The default value for an external MDisk is enterprise.

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.
-ext extent_size
(Required) Specifies the size of the extents for this group in MiB.
-size mdiskgrp_size
(Optional) Specifies the child pool capacity. The value must be a numeric value (and an integer multiple of the extent size).
-parentmdiskgrp mdiskgrp_id | mdiskgrp_name
(Optional) Specifies the parent pool from which the volume extents of the child pool are allocated when you create a child pool. The value must be an mdiskgrp_id or mdiskgrp_name.
-warning disk_size | disk_size_percentage%
(Optional) Generates a warning when the used disk capacity in the storage pool first exceeds the specified threshold. You can specify a disk_size integer, which defaults to megabytes (MiB) unless the -unit parameter is specified; or you can specify a disk_size%, which is a percentage of the storage pool size. To disable warnings, specify 0 or 0%. The default value is 0.
-unit b | kb | mb | gb | tb | pb
(Optional) Specifies the data units for the -warning parameter.
-easytier on | off | auto | measure
(Optional) Specifies whether the Easy Tier® function is active for this storage pool, or if it is automatically determined. auto is the default value. -easytier is active in storage pools with multiple tiers and is balance with single tiers.
Note:
  • If -easytier is set to auto, the system automatically enables Easy Tier functions when the storage pool contains MDisk from more than one tier, and enables automatic rebalancing when the storage pool contains an MDisk from only one tier.
  • If -easytier is set to on, then Easy Tier functions are active.
  • If -easytier is set to off, then Easy Tier functions are inactive.
  • If -easytier is set to measure Easy Tier statistics are collected but Easy Tier management is disabled. (No extents are moved by Easy Tier).
auto equates to:
  • on if Easy Tier is licensed or no license is required.
  • off if Easy Tier is not licensed and a license is required.
Specifying -easytier on enables Easy Tier:
  • Management of both single-tier and multitier pools
  • Auto rebalance
Extents are moved to balance the I/O load on the MDisks in the pool.
-owner owner_type
(Optional) Specifies the owner type required for vVol child pools. The value must be vvol_child_pool for the system to use as a vVol storage container.
-encrypt yes | no
(Optional) Specifies the encryption status for this storage pool. The values are yes or no.
Remember:
  • If you do not specify -encrypt and encryption is enabled, the system defaults to -encrypt yes (the default encryption setting).
  • When you create a child pool in an encrypted parent pool, the value must not be no. (All other permutations are permitted).
  • When you create a data reduction child pool, you cannot specify -encrypt. The encryption status is inherited from the parent pool.
-datareduction yes | no
(Optional) Specifies whether the storage pool is a data reduction storage pool. The values are yes or no. A value of no specifies that the storage pool is a standard storage pool.
-provisioningpolicy provisioning_policy_id | provisioning_policy_name
(Optional) The name or ID of the provisioning policy for the pool.
-etfcmoverallocationmax percentage | off
(Optional) Sets the maximum over allocation which Easy Tier can migrate onto FlashCore Module arrays, when the array is used as the top tier in a multitier pool. The value acts as a multiplier of the physically available space. The allowed values are a percentage in the range of 100% (default) to 400% or off. Setting the value to off disables this feature.
-vdiskprotectionenabled yes | no
(Optional) Specifies whether volume protection is enabled for this storage pool. The default value is yes, except for child pools where the default value is inherited from the parent pool.
Note: Volume protection can not be enabled for pools with the owner vvol_child_pool. Thus, the default value is no while creating a pool with this owner and the mkmdiskgrp command fails if the argument -vdiskprotectionenabled yes is passed and the pool has the owner vvol_child_pool.
-noquota
(Optional) Creates a child pool without a size.
Note: This parameter is required if -datareduction yes is specified while creating a child pool.
-replicationpoollinkuid replication_pool_link_uid
(Optional) Specifies the replication pool link unique identifier (UID) value to assign to the new pool. This value is used for linking pools between local and remote systems that use policy-based replication.

Description

Table 1. Parameter differences for child pools and storage pools
Parameter Child pool usage Storage pool usage
-name Optional Optional for both parent pools and child pools.
-mdisk Cannot be used with child pools. Optional
-tier Cannot be used with child pools. Optional
-easytier Cannot be used with child pools. Optional
-size

Optional. Cannot be used with -noquota or -datareduction child pools.

 Cannot be used with parent pools.
-parentmdiskgrp Mandatory Cannot be used with parent pools.
-ext Cannot be used for child pools. Mandatory
-unit Optional Optional for both parent pools and child pools.
-warning Optional for traditional child pools. Cannot be used with child pools that are data reduction pools. Optional for both parent pools and child pools.
-encrypt Optional. Cannot be used with child pools that are data reduction storage pools. Optional for both parent pools and child pools.
-datareduction Optional. Can be used to create a traditional child pool when the value is set to no. Can be used to create a data reduction child pool when the value is set to yes, and -parentmdiskgrp is a parent data reduction pool. Data reduction pools must be a parent pool.
-noquota Optional. Cannot be used with -size, -warning, or -encrypt. Cannot be used with parent pools.

The mkmdiskgrp command creates a new storage pool and assigns the storage pool name if specified. The ID of the new storage pool is returned if the command is successful. Storage pools are collections of managed disks. Each storage pool is divided into chunks, called extents, which are used to create volumes.

Optionally, you can specify a list of managed disks that are added to this storage pool. These managed disks cannot belong to another storage pool, and they must have a mode of unmanaged. Use the lsmdiskcandidate command to get a list of suitable candidates. If -tier is specified, it applies to all of the MDisks.

Each managed disk that is a member of this group is split into extents. The storage that is available on these disks is added to a pool of extents that is available in this group. When a volume is created from this group, free extents from the pool are used, in accordance with the policy used when the volume was first created.

Subsequently, all managed disks added to this group are split into extents of the same size as the size that is assigned to the group.

When you choose an extent size, be aware of the amount of storage you want to virtualize in this group. The system maintains a mapping of extents between volumes and managed disks. One system can virtualize the following number of extents:
  • 64 TB - if all storage pools have extent sizes of 16 MiB.
  • 2 PB - if all storage pools have extent sizes of 512 MiB.
  • 32 PB - if all storage pools have extent sizes of 8192 MiB.
Important: The extent size for the storage pool can also limit volume size. Consider the maximum volume size that you want to use when you create storage pools. Refer to the information on creating storage pools for a comparison of the maximum volume capacity for each extent size. The maximum is different for thin-provisioned volumes.
Note: When an image mode volume is created, the storage pool increases in capacity by the size of the image mode volume (not the MDisk capacity) because the image mode volume might be smaller than the MDisk itself. If an extent is migrated from the image mode volume or MDisk to elsewhere in the group, the volume becomes a striped volume (no longer image mode). At this point, the available capacity might increase because the extra capacity available on the MDisk (for example, the capacity that was not part of the image mode volume) becomes available.
Remember: When you use the -mdisk parameter, the storage pool is not created if one of the MDisks is a SAS MDisk.

When you specify -name pool_name if you do not also specify -parentmdiskgrp, you create a parent pool where pool_name is the name of the new storage pool. When you specify -name pool_name, if you also specify -parentmdiskgrp and a size for it or -noquota, you create a child pool where pool_name is the name of the new storage pool.

Note:

A data reduction pool is created by using the -datareduction parameter set to yes. The pool can be used to create standard-provisioned, thin or compressed volumes, or volume copies.

There is a maximum number of four data reduction pools in a system. When this limit is reached, creating any further pools with -datareduction set to yes is not possible.

The -datareduction parameter can be used to create a child pool that is a data reduction pool. The parent pool must also be a data reduction pool.

In most cases volume protection is applied on a volume level, but a volume might have more than one copy, with copies in different storage pools, which in turn can have different protection settings. A volume is protected when it has one or more copies in a storage pool that has vdisk_protection_status active.

For rmvdiskcopy, volume protection is applied on a volume copy level, but only when you delete the last volume copy. When you delete one of two volume copies, volume protection is not applied. It means that a volume copy might be deleted from a protected storage pool and leaves a remaining copy in an unprotected storage pool that might then later be deleted without volume protection checks.

An invocation example

This example adds a list of MDisks to the storage pool.

mkmdiskgrp -mdisk mdisk0:mdisk1:mdisk2:mdisk3 -ext 4096

The resulting output:

MDisk Group, id [0], successfully created