Select Page

What is a Logical Unit Number (LUN)?

What is a Logical Unit Number (LUN)?

A Logical Unit Number (LUN) is a number used for recognizing a logical unit related to computer storage. A logical unit is a device which can be addressed by computer network protocols like Fibre Channel (FC), Small Computer System Interface (SCSI), Internet SCSI (iSCSI), File Transfer Protocol (FTP) and other such related protocols.

Logical Unit Numbers are necessary for managing block storage arrays in a Storage Area Network (SAN). Typically a LUN can be utilized in processes with any component supporting read/write. The term LUN was termed way back from the days SCSI was used, where each device was identified with a logical number and the maximum number was limited to eight at that time. Now, servers with more LUNs are the trend and they are getting connected to a conventional internal SCSI disk array. Conversely, the fundamental of storage for the server is referred to as a LUN.

A logical unit number identifies a specific hard disk drive or a hard disk array in the storage environment with the help of a logical unit. So, taking this scenario into consideration a LUN could refer entire RAID set, a single drive or partition or multiple hard disk. In each case, the logical unit is treated as if it is a single device and is recognized by the LUN.

Understanding this term in a more technological way, let us assume a standard disk array which has several SCSI ports and all of them are assigned with respective target address. RAID formatting is applied onto the disk array and is partitioned into various storage units. So, a logical unit is configured to each volume and like-so several logical units are formed from several volumes.

In the same way, a disk drive has a single SCSI port and so has only one target with a single logical unit with zero LUN. Here it must be noted that zero signifies the entire storage of the disc drive. So, a number in-between zero and seven is allotted to each device in an 8-bit bus or a number between 8 and 16 is assigned to the device on a 16-bit bus.

When a device initiates an I/O request, it is called as an Initiator and the device which executes the request is known as a target. An individual target has the ability to interconnect with up to eight components or more, by using a controller. These components are called as Logical units and the SCSI LUN can be addressed with a combination of a target ID, disk ID, Controller ID and also a slice ID.

Recent Posts

What to Consider when Implementing DRaaS for ransomware protection

What to Consider when Implementing DRaaS for ransomware protection

According to Gartner, downtime costs more than $5,600 a minute; therefore, every business needs a reliable means of backup and disaster recovery. Disaster Recovery as a service (DRaaS) provides recovery in the cloud and is a cost-effective and highly efficient...

Downtime Cost: How to Calculate and Minimize it

Downtime Cost: How to Calculate and Minimize it

Downtime is bad for business. When applications, data and services are unavailable, business is disrupted, customers and stakeholders are unhappy, and regulatory authorities fine you. The true cost of unplanned downtime goes beyond lost revenue. How does one calculate...

Disaster Recovery as a Service (DRaaS) or On-Site DR Appliance?

Disaster Recovery as a Service (DRaaS) or On-Site DR Appliance?

Disaster Recovery-as-a-Service (DRaaS) delivers serverless recovery capabilities while disaster recovery (DR) appliances provide the on-prem secondary site that facilitates quick recovery. Which of the two is the best fit for you? Both deployment options have their...

FC SAN vs iSCSI SAN: What’s the Difference?

FC SAN vs iSCSI SAN: What’s the Difference?

Storage area networks (SANs) are a permanent fixture in corporate data centers used to host high-performance block-level structured workloads such as databases, applications, etc. If you’re familiar with SAN systems, then you’ve heard of Fibre Channel (FC) and iSCSI...

You May Also Like

Subscribe To Our Newsletter

Join our mailing list to receive the latest news, updates, and promotions from StoneFly.

Please Confirm your subscription from the email