chiogrp

Use the chiogrp command to modify I/O group properties or enable maintenance mode.

Syntax

Read syntax diagramSkip visual syntax diagram chiogrp -namenew_name-featureflashmirrorraidsnapshot-sizememory_size-kb-maintenanceyesnoio_group_idio_group_name

Parameters

-name new_name
(Optional) Specifies the name to assign to the I/O group. The -name parameter cannot be specified with the -feature, -size, or -kb parameters.
-feature flash | mirror | raid| snapshot
(Optional) Specifies the feature to modify the amount of memory for RAID arraysor volume mirroring. You must specify this parameter with the -size parameter. You cannot specify this parameter with the -name parameter.
  • flash specifies the amount of memory that is used for FlashCopy®.
  • mirror specifies the amount of memory that is used for volume mirroring operations.
  • raid specifies the amount of memory that is used for RAID arrays.
  • snapshot specifies the amount of memory that is used for volume snapshots.
-size memory_size
(Optional) Specifies the amount of memory that is available for the specified RAID arrays, Copy Services, or volume mirroring function. Valid input is 0 or any integer. The default unit of measurement for this parameter is MiB. Use the -kb parameter to override the default. You must specify this parameter with the -feature parameter. You cannot specify this parameter with the -name parameter.
-kb
(Optional) Changes the units for the -size parameter from MiB to KiB. If you specify this parameter, the -size memory_size value must be any number divisible by 4. You must specify this parameter with the -feature and -size parameters. You cannot specify this parameter with the -name parameter.
-maintenance yes | no
(Optional) Enable maintenance mode for the I/O group. This is used for some service procedures. After you enter maintenance mode, it continues until either:
  • It is explicitly cleared.
  • Thirty minutes elapse.
io_group_id | io_group_name
(Required) Specifies the I/O group to modify.

Description

The chiogrp command modifies the I/O group properties, or enables maintenance mode.

Use the -feature and -size parameters (together) to change the amount of memory available in the I/O group to one of the following types:
  • FlashCopy
  • Volume mirroring
  • RAID
  • snapshot
For example: 
chiogrp -feature flash -size 40 0
The amount of memory can be decreased or increased. Consider the following memory sizes when you use this command:
  • The default amount of memory for FlashCopy is 20 MiB.
  • The default memory size for mirrored volumes is 20 MiB.
  • The default memory size for RAID arrays is 40 MiB.
  • The default amount of memory for volume snapshots is 0 MiB.
  • The maximum amount of memory for volume snapshots.
This table demonstrates the amount of memory that is required for copy services and volume mirroring. For the listed grain size, each 1 MiB of memory provides the indicated volume capacities.
Table 1. Memory that is required for copy services and volume mirroring
Feature Grain size 1 MiB of memory provides the following volume capacity for the specified I/O group
FlashCopy 256 KiB 2 TiB of total FlashCopy target volume capacity
FlashCopy 64 KiB 512 GiB of total FlashCopy target volume capacity
Incremental FlashCopy 256 KiB 1 TiB of total Incremental FlashCopy target volume capacity
Incremental FlashCopy 64 KiB 256 GiB of total Incremental FlashCopy target volume capacity
Volume mirroring 256 KiB 2 TiB of mirrored volumes

For multiple FlashCopy targets, you must consider the number of mappings. For example, for a mapping with a 256 KiB grain size, 8 KiB of memory allows one mapping between a 16 GiB source volume and a 16 GiB target volume. Alternatively, for a mapping with a 256 KiB grain size, 8 KiB of memory allows two mappings between one 8 GiB source volume and two 8 GiB target volumes.

After you create a FlashCopy mapping, if you specify an I/O group other than the I/O group of the source volume, the memory accounting goes towards the specified I/O group, not towards the I/O group of the source volume.

Note: For FlashCore Modules, the effective capacity should be used and not the physical capacity.

An invocation example to change the name of an existing I/O group to testiogrpone

chiogrp -name testiogrpone io_grp0

The resulting output:

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