chiogrp

Use the chiogrp command to modify the name of an I/O group, or the amount of memory that is available for RAID arrays, Copy Services, FlashCopy® services, or volume mirroring operations.

Syntax

Read syntax diagramSkip visual syntax diagram chiogrp -namenew_name-featureflashremotemirrorraid-sizememory_size-kb-maintenanceyesno-fctargetportmodedisabled transitionalenabled-forceio_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 | remote | mirror | raid
(Optional) Specifies the feature to modify the amount of memory for RAID arrays, Copy Services, or 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.
  • remote specifies the amount of memory that is used for remote copy processing. Remote copy includes Metro Mirror, Global Mirror, and HyperSwap®.
  • 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.
Note: Specifying remote changes the amount of memory that is available for remote copy processing. Any volume that is in a remote copy relationship uses memory in its I/O group, including master and auxiliary volumes, and volumes that are in inter-system or intra-system relationships.
-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.
-maintenanceyes | no
(Optional) Specifies whether the I/O group must be in maintenance mode. The I/O group must be placed in maintenance mode while performing service procedures on storage enclosures. After you enter maintenance mode, it continues until either:
  • It is explicitly cleared.
  • Thirty minutes elapse.
Note: Changing the maintenance mode on any I/O group changes the maintenance mode on all I/O groups.
-fctargetportmode disabled | transitional | enabled
(Optional) Specifies the Fibre Channel (FC) host port mode of the I/O group. The values are disabled, transitional, or enabled. The transitional state is an intermediate state where both the virtual ports and physical ports are enabled.
Note: NVMe over Fibre Channel is not supported in the disabled state and on some Fibre Channel adapters and platforms.
-force
(Optional) Specifies that an FC host port be disabled or enabled, even if disruption to host I/O might occur as a result. You can only specify -force with -fctargetportmode.
Important: Specifying -force might result in a loss of access. Use it only under the direction of your product support information.
io_group_id | io_group_name
(Required) Specifies the I/O group to modify. You can modify an I/O group by using the -name or the -feature parameter.

Description

The chiogrp command modifies the name of an I/O group or the amount of memory that is available for RAID arrays, Copy Services, or volume mirroring.

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
  • Remote copy, including Metro Mirror, Global Mirror, and HyperSwap.
For example: 
chiogrp -feature flash -size 40 0

You can assign a name to an I/O group or change the name of a specified I/O group. You can change the amount of memory that is available for RAID arrays, Copy Services, or volume mirroring operations by specifying the -feature flash | remote | mirror parameter - and a memory size. For volume mirroring and Copy Services (FlashCopy, Metro Mirror, Global Mirror, and HyperSwap), memory is traded against memory that is available to the cache.

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 amount of memory for remote copy (which includes Metro Mirror, Global Mirror, and HyperSwap) is 20 MiB.
  • The default memory size for mirrored volumes is 20 MiB.
  • The default memory size for RAID arrays is 40 MiB.
  • The maximum amount of memory that can be specified for FlashCopy is 512 MiB. For 64-bit systems, the maximum is 2048 MiB.
  • The maximum amount of memory for remote copy (which includes Metro Mirror, Global Mirror, and HyperSwap) is 512 MiB.
  • The maximum memory size that can be specified for mirrored volumes is 512 MiB.
  • The maximum memory size for RAID arrays is 512 MiB.
The maximum combined amount of memory across all features is 552 MiB.
Note: For 64-bit systems, the maximum is 2600 MiB. Some systems that are running 64-bit mode might have 2 GiB of bitmap space to use for FlashCopy, which is enough for 4 PiB of data space to be used per I/O group. For example, Metro Mirror, Global Mirror, Volume Mirroring, and RAID share 552 MiB of bitmap space, which is enough to use 1080 PiB of data space per I/O group. Older systems, such as those running 32-bit code, might be subject to a 740 MiB limit.
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
Metro Mirror and Global Mirror 256 KiB 2 TiB of total Metro Mirror and Global Mirror volume capacity
HyperSwap 256 KiB 2 TiB of total HyperSwap volume capacity
Note: For 2 TiB of HyperSwap volume capacity, 1 MiB must be assigned in each caching I/O group.
FlashCopy 256 KiB 2 TiB of total FlashCopy source volume capacity
FlashCopy 64 KiB 512 GiB of total FlashCopy source volume capacity
Incremental FlashCopy 256 KiB 1 TiB of total Incremental FlashCopy source volume capacity
Incremental FlashCopy 64 KiB 256 GiB of total Incremental FlashCopy source volume capacity
Volume mirroring 256 KiB 2 TiB of mirrored volumes
Table 2 provides the approximate memory cost for each array in an I/O group, where MS is the size of each member drive and MC is the number of member drives in the array. For multiple arrays in an I/O group, adding the costs together to get the RAID feature size for the I/O group.
Table 2. RAID level bitmap memory costs
Level Member count Approximate capacity Redundancy Approximate bitmap memory cost
RAID-0 1-8 MC * MS None (1 MiB per 2 TiB of MS) * MC
RAID-1 2 MS 1 (1 MiB per 2 TiB of MS) * (MC/2)
RAID-5 3-16 (MC-1) * MS 1 1 MiB per 2 TiB of MS with a strip size of 256 KiB; double with strip size of 128 KiB.
RAID-6 5-16 Less than (MC-2 * MS) 2
RAID-10 2-16 (evens) MC/2 * MS 1 (1 MiB per 2 TiB of MS) * (MC/2)
Note: The approximate bitmap memory cost has a margin error of 15% approximately. For example, the cost for a 256 KiB strip size for RAID-5 is ~1.15 MB for the first 2 TiB of MS.

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.

Scenario 1

If the I/O group contains:
  • At least one 8 GiB node.
  • At least one thin-provisioned or compressed volume in a data reduction pool.
  • A FlashCopy bitmap size for that I/O group set beyond 1.5 GiB.
The command fails due to insufficient resources available.

An invocation example to create a new I/O group testiogrpone

chiogrp -name testiogrpone io_grp0

The resulting output:

No feedback

An invocation example for changing the amount of FlashCopy memory in io_grp0 to 30 MiB

chiogrp -feature flash -size 30 io_grp0

The resulting output:

No feedback

An invocation example for changing the amount of RAID memory in I/O group 0 to 512 MiB

chiogrp -feature raid -size 512 0

The resulting output:

No feedback