The overall physical storage of a platform’s SAS disks is divided into logical virtual disks, in order to provide flexibility in allocating storage space. These virtual disks can then be assigned to the various partitions on the platform as desired. Virtual disks are identified by logical unit numbers (LUNs). Different LUNs represent different instances of storage space for use by different partitions.
At minimum, the required size of the partition’s LUN is the storage size of the operating system itself.
In addition to the boot LUN, seven data LUNs are supported. This enables you to limit the size of the boot LUN. However, you might want to associate application data with the partition containing the operating system by configuring the boot LUN’s space as multiple disk drives (for example C: and K:). In this case, you must also include this application data storage size in the partition LUN along with the operating system size. In this case the LUN size calculation is as follows:
Required OS size + additional optional application data size
Minimum required LUN sizes for partition images depend on a number of factors, most importantly
Whether the partition will run Windows or Linux
(Refer to Windows and Linux operating system documentation for specific information about required LUN sizes.)
The amount of memory
The number of processor cores
However, other factors are also involved, including
Operating system and application configurations in the blueprint and gold image
Whether the partition image is supplied by Unisys or the customer
Whether the partition image boots from internal or external storage
If the partition image boots from external storage, whether the external storage is accessed via iSCSI or fibre channel
General guidelines for minimum LUN sizes are as follows:
Unisys-supplied gold image, with the boot volume on internal storage
Windows: 60 GB
Linux: 20 GB
If your partition image has been configured with large amounts of memory (for example, 3 TB), 110 GB is preferable for Windows, and Linux will require a larger LUN size as well.
Customer-supplied gold image, with the boot volume on internal storage
Use a LUN size of at least the size of the original disk size of the operating system that you captured.
Linux gold image, with the boot volume on an external storage device accessed over iSCSI
20 GB.
Boot volume on an external storage device accessed over fibre channel
Generally, a small LUN is needed to contain the necessary drivers—for example, 1 GB.
As a general guideline: If all of an enterprise partition platform’s memory, processor cores (with hyperthreading enabled), NICs, HBAs, and all 7 data LUNs are assigned to a Windows partition during commissioning, then a LUN of about 110 GB is required.