Adding a copy to a basic volume

The addvdiskcopy command adds a copy to an existing basic volume, which changes a nonmirrored volume into a mirrored volume. In the management GUI, select Volumes and right-click the basic volume and select Add Volume Copies.

Creating mirrored copies of a basic volume allows the volume to remain accessible even when a managed disk (MDisk) that the volume depends on becomes inaccessible. You can create copies of a volume either from different pools or by creating an image mode copy of the volume. Copies allow for availability of data; however, they are not separate objects. You only can create or change mirrored copies from the volume. The system disables adding a copy of a volume if the selected volume is completing quick initialization. After the quick initialization completes, you can create a mirrored copy of the volume.

In addition, you can use volume mirroring as an alternative method of migrating volumes between pools. For example, if you have a basic volume in one pool, you can add a new copy of the volume by specifying the second pool for that volume copy. After the copies are synchronized, you can delete the copy in the first pool. While the volume is migrated to the second pool, it remains online during the migration.

This alternative method of migrating volumes has the following advantages:

• Access to the volume data is not lost if the second pool goes offline during the migration.
• The speed of the migration can be adjusted, by using the volume synchronization rate, and the migration can be paused.
• The migration can be ended by deleting the volume copy in the second pool before migration completes.
• The pools can have different extent sizes.

This alternative method has the following limitations:

• You cannot use this method for volumes that are already mirrored.
• This method requires more manual steps.
• Write I/O performance is slightly affected during the migration because the mirrored copies must be kept synchronized.

For image copies, you must specify the virtualization type by using the -vtype parameter and an MDisk that is in unmanaged mode by using the -mdisk parameter. This MDisk must be in the unmanaged mode. The -vtype parameter is optional for sequential (seq) and striped volumes. The default virtualization type is striped.

Use the syncrate parameter to specify the rate at which the volume copies will resynchronize after loss of synchronization.

addvdiskcopy -mdiskgrp 0 vdisk8