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
chiogrp { [ -name new_name ] | | [ -feature { flash | remote | mirror | raid } -size memory_size [ { -kb } ] ] } [ -maintenance [ { yes | no } ] ] [ -fctargetportmode { disabled | transitional | enabled } ] [ -force ] { io_group_id | io_group_name }
Parameters
- -namenew_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.
- -featureflash | 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.
- -sizememory_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 megabytes (MB); you can use the kilobytes
-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 megabytes
(MB) to kilobytes (KB). If you specify this parameter, the -sizememory_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) 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.
- -fctargetportmodedisabled | transitional | enabled
- (Optional) Specifies the Fibre Channel (FC) host port mode of the I/O group. The values are
disabled, transitional, or enabled.
- -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 -featureflash | remote | mirror parameter -
and a memory size. For volume mirroring and
Copy Services (Flash Copy®, 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 MB.
- The default amount of memory for remote copy
(which includes Metro Mirror, Global Mirror, and HyperSwap) is 20 MB.
- The default memory size for mirrored volumes is 20 MB.
- The default memory size for RAID arrays is 40 MB.
- The maximum amount of memory that can be specified for FlashCopy® is 512 MB. For 64-bit systems,
the maximum is 2048 MB.
- The maximum amount of memory for remote copy
(which includes Metro Mirror, Global Mirror, and HyperSwap) is 512 MB.
- The maximum memory size that can be specified for mirrored volumes is 512 MB.
- The maximum memory size for RAID arrays is 512 MB.
The maximum combined amount of memory across all features is 552 MB.
Note: For 64-bit
systems, the maximum is 2600 MB. Some systems
running 64-bit mode might have 2 GB of bitmap space to use for FlashCopy, which is enough for 4 PB
of data space to be used per I/O group. For example, Metro Mirror, Global Mirror, Volume Mirroring,
and RAID share 552 MB of bitmap space, which is enough to use 1080 PB of data space per I/O group.
Older systems, such as those running 32-bit code, might be subject to a 740 MB limit.
Memory required for RAID arrays, Copy Services, and volume mirroring demonstrates the amount of memory
that is required for RAID arrays, Copy Services, and volume mirroring. Each 1 MB of memory provides
the following volume capacities and grain sizes:
Table 1. Memory required for RAID arrays, Copy Services, and volume mirroring| Feature |
Grain size |
1 MB of memory provides the following volume capacity for the specified I/O
group |
|---|
| Metro Mirror and Global Mirror |
256 KB |
2 TB of total Metro Mirror and Global Mirror volume capacity |
| HyperSwap® |
256 KB |
2 TB of total HyperSwap® volume capacity Note: For 2 TB of HyperSwap® volume capacity, 1 MB must be assigned in each
caching I/O group.
|
| FlashCopy |
256 KB |
2 TB of total FlashCopy source volume
capacity |
| FlashCopy |
64 KB |
512 GB of total FlashCopy source
volume capacity |
| Incremental FlashCopy |
256 KB |
1 TB of total Incremental FlashCopysource
volume capacity |
| Incremental FlashCopy |
64 KB |
256 GB of total Incremental FlashCopy source
volume capacity |
| Volume mirroring |
256 KB |
2 TB of mirrored volumes |
RAID level comparisons provides an example of RAID level comparisons with their bitmap memory cost,
where MS is the size of the member drives and MC is the number
of member drives.
Table 2. RAID level comparisons| Level |
Member count |
Approximate capacity |
Redundancy |
Approximate bitmap memory cost |
|---|
| RAID-0 |
1-8 |
MC * MS |
None |
(1 MB per 2 TB of MS) * MC |
| RAID-1 |
2 |
MS |
1 |
(1 MB per 2 TB of MS) * (MC/2) |
| RAID-5 |
3-16 |
(MC-1) * MS |
1 |
1 MB per 2 TB of MS with a strip size of 256 KB; double with strip size of 128
KB. |
| RAID-6 |
5-16 |
less than (MC-2 * MS) |
2 |
|
| RAID-10 |
2-16 (evens) |
MC/2 * MS |
1 |
(1 MB per 2 TB of MS) * (MC/2) |
Note: There is a margin of error on the approximate bitmap memory cost of approximately
15%. For example, the cost for a 256 KB strip size for RAID-5 is ~1.15 MB for the first 2 TB of MS.
|
For
multiple Flash Copy® targets, you must consider the number of mappings.
For example, for a mapping with a 256 KB grain size, 8 KB of memory
allows one mapping between a 16 GB source volume and a 16 GB target
volume. Alternatively, for a mapping with a 256 KB grain size, 8 KB
of memory allows two mappings between one 8 GB source volume and two
8 GB target volumes.
Afte you create a Flash Copy® 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.
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 Flash
Copy® memory in io_grp0 to 30 MB
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 MB
chiogrp -feature raid -size 512 0
The resulting output:
No feedback