Expand or shrink volumes

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

Expand volumes

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

To expand a volume by using the CLI, see the chvolume command.

Note: If the volume being expanded is configured for high availability, and HA is currently suspended, then some host operating systems might fail to detect the resized device. In this case, remove the host paths to the offline copy of the volume, or wait for HA to be re-established before continuing.

Shrink volumes

Volumes can be reduced in capacity, if it is necessary. 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:
  1. 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.
  2. 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.
  3. 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 GUI 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:
  • Volumes in a data reduction pool.
  • A target volume in FlashCopy mappings. 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.
  • The capacity of replicated volumes.

To shrink a volume by using the CLI, see the shrinkvdisksize command.