What is LUN (Logical Unit Number) in Computer Systems?

LUN stands for Logical Unit Number. It is a number that is assigned to a storage device, such as a hard drive or a tape drive, in a computer system. The LUN is used to identify the device and to distinguish it from other devices in the system.

For example, if a computer system has two hard drives, each hard drive would be assigned a unique LUN number, such as LUN 0 and LUN 1. This allows the operating system and other software to access the correct device when performing I/O operations.

LUNs are typically used in storage area networks (SANs) and other clustered storage environments, where multiple storage devices are connected to multiple servers. In these environments, each server may have multiple LUNs assigned to it, allowing the server to access multiple storage devices.

It's important to note that LUNs are not physical devices, but rather a logical identifier for a physical device. A LUN can be mapped to a physical device, such as a hard drive or a tape drive, and can be used to access the device from multiple servers in a clustered environment.