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 { [ -namenew_name ] | [ -feature { flash | remote | mirror | raid } -sizememory_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.
The
transitional state is an intermittent 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
-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 that are 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.
This table 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. Summary of RAID level bitmap memory costs
| 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 FlashCopy
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.
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 GB 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 GB.
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 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