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 }
-sizememory_size [ { -kb } ] ]
} [ -maintenance
[ { yes | no
} ] ] { 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.
- 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. 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.
Table 1 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 |
Table 2 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