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.
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.
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.
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 |
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.
chiogrp -name testiogrpone io_grp0
The resulting output:
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chiogrp -feature flash -size 30 io_grp0
The resulting output:
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chiogrp -feature raid -size 512 0
The resulting output:
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