Modifying the amount of available memory for Copy Service and VDisk Mirroring features using the CLI

You can use the command-line interface (CLI) to modify the amount of memory that is available for the VDisk Mirroring feature and the FlashCopy®, Metro Mirror, or Global Mirror Copy Services features.

Table 1 provides an example of the amount of memory that is required for VDisk Mirroring and each Copy Service feature.

Table 1. Memory required for VDisk Mirroring and Copy Services
Feature	Grain size	1 MB of memory provides the following VDisk capacity for the specified I/O group
Metro Mirror or Global Mirror	256 KB	2 TB of total Metro Mirror and Global Mirror VDisk capacity
FlashCopy	256 KB	2 TB of total FlashCopy source VDisk capacity
FlashCopy	64 KB	512 GB of total FlashCopy source VDisk capacity
Incremental FlashCopy	256 KB	1 TB of total incremental FlashCopy source VDisk capacity
Incremental FlashCopy	64 KB	256 GB of total incremental FlashCopy source VDisk capacity
VDisk Mirroring	256 KB	2 TB of mirrored VDisk capacity
Notes: For multiple FlashCopy targets, you must consider the number of mappings. For example, for a mapping with a grain size of 256 KB, 8 KB of memory allows one mapping between a 16 GB source VDisk and a 16 GB target VDisk. Alternatively, for a mapping with a 256 KB grain size, 8 KB of memory allows two mappings between one 8 GB source VDisk and two 8 GB target VDisks. When creating a FlashCopy mapping, if you specify an I/O group other than the I/O group of the source VDisk, the memory accounting goes towards the specified I/O group, not towards the I/O group of the source VDisk. For VDisk Mirroring, the full 512 MB of memory space provides 1 PB of total VDisk Mirroring capacity. In this table, capacity refers to the virtual capacity of the VDisk. For space-efficient VDisks with different virtual capacities and real capacities, the virtual capacity is used for memory accounting.

To modify and verify the amount of memory that is available, perform the following steps:

Issue the following command to modify the amount of memory that is available for VDisk Mirroring or a Copy Service feature:
svctask chiogrp -feature flash|remote|mirror -size memory_size io_group_id | io_group_name
where flash|remote|mirror is the feature that you want to modify, memory_size is the amount of memory that you want to be available, and io_group_id | io_group_name is the ID or name of the I/O group for which you want to modify the amount of available memory.
Issue the following command to verify that the amount of memory has been modified:
svcinfo lsiogrp object_id | object_name
where object_id | object_name is the ID or name of the I/O group for which you have modified the amount of available memory.

The following information is an example of the output that is displayed.
```
id 0
name io_grp 0
node_count 2
vdisk_count 28
host_count 2
flash_copy_total_memory 20.0MB
flash_copy_free_memory 20.0MB
remote_copy_total_memory 20.0MB
remote_copy_free_memory 20.0MB
mirroring_total_memory 10.0MB
mirroring_free_memory 10.0MB
```