Expanding volumes

You can use the management GUI or the command-line interface (CLI) to expand the capacity of a volume.

The system supports expanding the size of a volume concurrent with I/O operations, when supported by the host operating system.

You can expand volumes for the following reasons:

To increase the available capacity on a particular volume that is already mapped to a host.
To increase the size of a volume so that it matches the size of another volume so that it can be used in a FlashCopy® mapping.
For volumes in non-incremental FlashCopy mappings, you can increase the capacity regardless of whether the volume is the source or target volume. For volumes in incremental FlashCopy mappings, both the source and target volumes can be expanded, but the capacity of the target volume must be expanded first.

To expand a volume, see expandvdisksize command.

Shrinking volumes

You can reduce the capacity of a compressed or uncompressed volume by using the management GUI or the command-line interface (CLI).

Volumes can be reduced in capacity, if it is necessary. You can make a target or auxiliary volume the same capacity as the source or master volume when you create FlashCopy mappings,. However, if the volume contains data, do not shrink the size of the disk. The system disables shrinking a volume if the selected volume is performing quick initialization. After the quick initialization completes, you can shrink the volume.

Attention:

It is difficult to anticipate how an operating system or file system uses the capacity in a volume. When you shrink a volume, capacity is removed from the end of the disk, whether or not that capacity is in use. Even if a volume has available capacity, do not assume that only unused capacity is removed when you shrink a volume.
If the volume contains data that is being used, do not attempt under any circumstances to shrink a volume without first backing up your data.
For performance reasons, some operating systems or file systems use the outer edge of the disk.

You can use the shrinkvdisksize command or the management to shrink the usable capacity that is provisioned to the particular volume by the specified amount. You can also shrink the provisioned capacity of a thin-provisioned volume without altering the usable capacity that is assigned to the volume.

You cannot shrink the following types of volumes:

Mirrored volumes that have at least one standard-provisioned volume copy.
Volumes in a data reduction pool.
A target volume in FlashCopy mappings cannot be shrunk. However, you can shrink a source volume, if the starting capacity of the FlashCopy mapping is not greater than the proposed capacity for the source volume. The management GUI filters target volumes that can be shrunk and disables the shrink action for those volumes that do not meet the criteria. If you are using the command-line interface, use the lsfcmap command to display the starting capacity (start_capacity parameter) of the FlashCopy mapping. This parameter indicates the capacity that was used the last time the FlashCopy operation was completed.

To shrink a volume, see shrinkvdisksize command.