topic Re: Lun's in Disk Enclosures

Lun's

Adam Darwin — Thu, 08 Feb 2001 15:47:03 GMT

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.

Re: Lun's

MARTINACHE — Thu, 08 Feb 2001 15:56:41 GMT

Hi,

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.

Regards,

Patrice

Re: Lun's

Jason VanDerMark — Thu, 08 Feb 2001 16:24:40 GMT

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.