Using Auto-Carving for Multi LUN Support

When the Auto-Carving policy is on, any unit larger than a specified size (known as the carve size) is created as multiple volumes that can be addressed by the operating system as separate volumes. These chunks are sometimes known as multiple LUNs (logical units). However, throughout the 3ware documentation, they are referred to as volumes.

For example, using the default carve size of 2 TB, if the unit is 2.5 TB then it will contain two volumes, with the first volume containing 2TB and the second volume containing 0.5 TB. If the unit is 5.0 TB then it will contain 3 volumes, with the first two volumes containing 2 TB each and the last volume containing 1 TB. (Note: If a specific Boot Volume was also specified in 3BM, the first volume will be the size specified for the Boot Volume, and then the carve size will be applied to the remainder of the unit. For more information, see Boot volume size.)

Each volume can be treated as an individual disk with its own file system. The default carve size is 2 TB; you can change this to a setting in the range of 1 TB to 2 TB (1024 MB to 2048 MB). 3ware firmware supports a maximum of 8 volumes per controller, up to a total of 16 TB.

If you are migrating a unit to a size that is larger than the carve size and auto-carving is on, multiple volumes will be created.

The main use of auto-carving is to gain use of the full capacity in units greater than 2 TB. This is because Windows 2000, Windows 2003, Windows XP, and FreeBSD 4.x, do not currently recognize unit capacity in excess of 2 TB.

You must turn on the Auto-Carving policy before creating the unit. Units created with this policy turned off will not be affected by a change to the policy. If the policy is turned off later, units that have been carved into volumes will retain their individual volumes; existing data is not affected.

To use auto-carving

Enable the auto-carving feature. You can do so using 3DM, 3BM, or the 3ware CLI.

In 3DM, enable Auto-Carving at the bottom of the Management > Controller Settings page.

In 3BM, you enable Auto-Carving on the Settings > Controller Policies page.

In CLI, use the command tw_cli /cx set autocarve=on. For more information, see the 3ware 9000 Series Serial ATA RAID Controller CLI Guide.

Create a new unit or migrate an existing unit to include the drives you want to use.

With auto-carving enabled, if the combined capacity of the drives exceeds the carve size, a number of volumes will be created. When the carve size is the default of 2 TB, up to 8 individual 2 TB volumes will be created from the unit.

For example, a 5 TB unit would become 3 volumes; two 2 TB volumes and one 1 TB volume. (After creating as many volumes as possible of the specified carve size, any remainder will create a final volume.)

Verify the creation of the volumes through 3DM 2 or the CLI.

In 3DM 2, the number of volumes is shown on the Unit Details page.

Verify that the volumes appear in the operating system. They will appear as additional drives.