LUN storage: Working with a SAN's logical unit numbers

Introduction

In a SAN fabric, LUN storage is essential to the configuration of the environment and its performance. A LUN is a unique identifier given to separate devices, or logical units, so they can be accessed by a SCSI, iSCSI or Fibre Channel protocol. LUNs are key to disk array configuration because disks are typically defined in sets of RAID groups to protect against failure; however, those RAID groups can't be presented to the host. By assigning LUNs, all or a portion of a RAID group's capacity can be presented to the host as individual, mountable volumes.

For IT pros, implementing LUN storage involves a number of decisions, such as the number of LUNs to be created, what size they will be and what hardware the LUNs will live on. Additionally, techniques such as LUN masking and LUN zoning can be used to dictate which hosts have access to which LUNs.

This guide walks you through all these issues by explaining how LUN storage works, the basics of implementation and best practices for management.

1Understanding LUN storage-

LUN storage and how it works

At a basic level, LUNs are a reference to specific storage in a SAN. A LUN can represent a hard disk drive (HDD), a portion of an HDD or even a full storage array. LUNs are essential to the management and efficiency of your storage because they dictate which hosts will access which storage. The following links provide a closer look at how LUN storage works and how certain configurations can affect the performance of your storage environment.

2Implementing LUNs-

Best practices to ensure efficient LUN implementation

Because one LUN can be shared by numerous hosts or vice versa, you need to consider how big a LUN will be and how many LUNs a single host can access. Other important implementation considerations include which RAID levels get the best performance for their cost and whether to use technologies such as thin provisioning, tiering or data deduplication. The material below describes how to approach each of these decisions and their effect on a SAN environment.

3LUN management-

Using LUNs to ease storage management

Typically, all LUN storage can be managed through one software program that specifies the path between LUNs and hosts. However, management best practices can differ depending on the type of environment used -- Fibre Channel versus iSCSI storage, for example. The following tips outline some best practices for managing LUN storage.