Chapter 4: Logical Drives

Overview

A Logical Drive is defined as a region or combination of regions of unused space on the array(s) which makes the logical drives available to the host operating systems as a disk. You can create up to 512 logical drives. After an array has been created, this region is first marked as unassigned. One or more logical drives can be created in this region or an existing logical drive can be expanded using this region.

A logical drive can be created or expanded in 1 GB increments with a maximum total size per drive of 2,198 GBs. This corresponds to the SCSI 32-bit addressing limitation of 2 TB.

Important Before you create more than one logical drive, you must be sure that your host HBA and host operating system is setup to handle the desired number of logical drives (LUNs or Logical Unit Numbers). If your operating system does not support multiple logical drives, the host will only be able to see the first logical drive.

Important For Microsoft® Windows® NT there is a limitation of 231 logical drives. A hot fix is available from Microsoft. See Microsoft Knowledge Base Article-245637.

Terminology

The following table describes the terminology relating to logical drives.

Term

Description

 

 

Segmentation

Any logical drive can be expanded into any free region, so

 

it is possible to easily add capacity at any time. There is

 

no requirement that any additional space be contiguous.

 

Logical drive segmentation is completely transparent to the

 

host systems.

 

 

Availability

To accommodate hosts with multiple ports and multiple

 

host systems, you can restrict a logical drive’s availability

 

to a particular controller port. Access can be enabled or

 

disabled for each port of each controller.

 

 

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