Storage Area Network Information Center

Before you can decide if Storage Area Networks (SANs) are the right technology choice for your organization, it's helpful to compare the other technology options, including:

• Direct Attached Storage (DAS)
• Network Attached Storage (NAS)

Direct Attached Storage (DAS)

Historically, the standard way of connecting hosts to storage devices has been direct, one-to-one SCSI attachments. As more and more storage and servers are added to meet demands, a DAS environment can cause a proliferation of server and storage islands, creating a huge management burden for administrators, as well as inefficient utilization of resources. Data sharing in these environments is also severely limited.

The limitations and challenges of DAS are the reason many organizations today have chosen SAN or a combination of SAN and NAS solutions.

The Advantages of SAN over DAS

The most effective SANs provide a wide range of benefits and advantages over DAS, including:

• More effective utilization of storage resources through centralized access
• Simplified, centralized management of storage, reducing administrative workload to save time and money
• Increased flexibility and scalability through any-to-any storage and server connectivity
• Improved throughput performance to shorten data backup and recovery time
• Reduced LAN congestion due to removal of backups from production network
• Higher data availability for business continuance through a resilient network design
• Excellent scalability and investment protection allowing you to easily add more storage as your business needs demand
• Superior security for storage environments
• Non-disruptive business operations when you add or re-deploy storage resources
• Proven short- and long-term return on investment (ROI)

Storage Area Network

Network Attached Storage (NAS)

Unlike SANs that utilize a network of Fibre Channel switches, most NAS connections reside between workstation clients and the NAS file-sharing facility. These connections rely on the underlying corporate network infrastructure to function properly, which can lead to network congestion, particularly for larger data transfers. NAS solutions are typically configured as file-serving appliances accessed by workstations and servers through a network protocol such as TCP/IP and applications such as Network File System (NFS) or Common Internet File System (CIFS) for file access.

NAS storage scalability is often limited by the size of the self-contained NAS appliance enclosure. Adding another appliance is relatively easy, but sharing the combined contents is not. Because of these constraints, data backups in NAS environments typically are not centralized, and therefore are limited to direct attached devices (such as dedicated tape drives or libraries) or a network-based strategy where the appliance data is backed up to facilities over a corporate or dedicated LAN. Increasingly, NAS appliances are using SANs to solve problems associated with storage expansion, as well as data backup and recovery.

NAS does work well for organizations needing to deliver file data to multiple clients over a network. Because most NAS requests are for smaller amounts of data, data can be transferred over long distances efficiently.

Let Your Business Requirements Drive Your Technology Choice

Your business requirements will help you determine which technology is right for you. Despite their many differences, SAN and NAS can actually complement one another as each are suited for different types of applications. Increasingly, NAS appliances are using SANs to solve problems associated with storage expansion, and data backup and recovery. Although the two are complementary, NAS does not provide the full range of business benefits provided by SANs.

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