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Multi LUN Support and Auto-Carving

When the Auto-Carving policy is on, any unit larger than a specified size (known as the carvesize) is created as multiple chunks 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. Each volume can be treated as an individual disk with its own file system. The default carvesize is 2 TB; this size can be changed through the CLI. 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 carvesize and auto-carving is on, multiple volumes will be created.

Note: Using auto-carving can have an impact on performance.

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.

Note: Operating systems without this limitation include Linux 2.6 and FreeBSD 5.x. Microsoft plans to overcome this limitation in Win XP-64bit and Windows 2003, SP 1.
If you use a 64-bit operating system, there is no need to set the policy to be on unless you want to have multiple smaller volumes available to the operating system.

You must turn on the Auto-Carving policy before creating the unit. Units created with this policy turned off will not be affected. 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

  1. Enable the auto-carving feature. You can do so using 3DM, 3BM, or the 3ware CLI.
  2. 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.

  3. Create a new unit or migrate an existing unit to include the drives you want to use.
  4. With auto-carving enabled, if the combined capacity of the drives exceeds the carvesize, a number of volumes will be created. When the carvesize 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 carvesize, any remainder will create a final volume.)

  5. Verify the creation of the volumes through 3DM 2 or the CLI.
  6. In 3DM 2, the number of volumes is shown on the Unit Details page.

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

To set the size of volumes created with auto-carving


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