Disk Array

Published March 31, 2010

AAA Print

Overview

A disk array is a storage system that has multiple disk drives. A disk array is more than just a simple disk enclosure and includes the following features: disk array controllers, cache memory, disk enclosures, and a power supply.

Disk arrays come in five categories: network attached storage (NAS), storage area network array (SAN), monolithic SAN, storage virtualization, and utility SAN. Network Attached Storage arrays have their own Local Area Network (LAN) IP address and provide file level access to disk storage through protocols like the Common Internet File System (CIFS) and Network File System (NFS).

The second form of disk array is a modular storage area network array. They are different from LANs and wide area networks (WANs) and are dedicated networks that are used to connect one or many servers to storage resources. It provides block level access through Small Computer System Interface (SCSI) protocols through fibre channels and Internet SCSI (iSCSI).

Monolithic SAN arrays are the third type of disk arrays. Unlike with a Modular SAN, they are suited for operations that cannot fit into standard rack cabinets and as a result are mostly used by large scale enterprises. They are deployed in enterprise storage systems using Enterprise System Connections (ESCON) and Fiber Connection (FICON) protocols.

Storage virtualization runs on open source platforms and has software that adds functionality to a disk array controller for virtualization process.

Benefits

The main objective of disk arrays is to provide increased availability, resiliency, and maintainability of data storage. The usage of redundant components like controllers, power supplies, and fans help fulfill this objective. Disk arrays eliminate single points of failure and provide ultimate redundancy. Disk arrays have a high satisfaction rating and promote accountability.

How It Works

NAS disk arrays provide access to heterogeneous networks for file level data storage. The sole purpose is to supply file based data to devices across the network. They are implemented as a self contained system. NAS units store data, provide access to stored data, and implement file systems. It is controlled and configured by a browser from another computer. A dedicated computer that acts as a file server is also a NAS unit. NAS arrays are configured with one or more disks that are arranged logically into Redundant Array of Independent Disks (RAID) arrays.

NAS provides storage and file system while SAN only provides block level storage access, leaving the file system processing to the client. However, they can be mixed to form a SAN-NAS hybrid implementation. Therefore, both can be applied together in the same system using the same physical space.