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Adam Darwin
Occasional Contributor


I keep on coming across the term lun, to do with assigning disks in autoraids, etc. But, I don't really know what a lun is, could someone explain it to me please.
Respected Contributor

Re: Lun's


Here is the definition of a lun :

LUN=Logical Unit Number=Logical Drive

Logical Unit Number is portion of the array capacity that appears to the operating systems as a physical disk. The entire array capacity can be divided into up to eight Logical Drives. Only capacity that has been assigned to a Logical Drive is available to the operating system.


Jason VanDerMark
Trusted Contributor

Re: Lun's

A LUN is a Logical Unit Number it is used in a RAID or large storage array for addressing multiple disks located on a single SCSI channel. The LUNs allow multiple drives to exist on each SCSI port thus making large RAIDS and storage arrays possible. A LUN acts as an address to a certain drive or multiple drives on a certain SCSI port. For example, even though their are only 8 (0 through 7) scsi addresses available, the first of which is usually reserved for the controller and the last is normally not used. You are then left with 6 addresses. Each of these addresses can theoretically contain up to 8 LUNs and thus can contain 8 or more drives. As you can probably guess, LUNs are very important. As far as the ins and outs of LUN implementation, I can't help you but I am sure that the great people at HP would love to help you with it.

I am kind of new to SANs and large storage arrays myself. I welcome anyone else to add to my post or better yet, offer a better description of LUNs. I hope that this helps.
Tie two birds together, eventhough they have four wings, they cannot fly.