Author: Yogi Schulz
We’ve all heard the terms Storage Area Network (SAN) and Network Attached Storage (NAS). But what are the advantages and shortcomings of the two concepts? When should you deploy one over the other? How are these technologies evolving?
Once upon a time, servers relied exclusively on directly attached storage (DAS). This approach worked well enough so long as the data volume was small and the need to share data among applications running on different servers was rare.
However, as data volumes grew and the need to integrate data from multiple applications grew, operating systems gained the ability to make storage volumes connected to one server visible to another server. This approach became unwieldy to manage as the number of devices continued to grow.
Backups also became problematic. Buying a dedicated tape drive for each server became increasingly expensive and resulted too much running around to mount and retrieve tape cartridges. Backing up the storage of one server through the local area network to a tape drive connected to another server is excruciatingly slow and creates server availability problems.
Origin of SAN and NAS
Both SAN and NAS technologies were developed to help organizations manage growing volumes of data without compromising performance and to contain operational complexity. SAN tended to be adopted by larger organizations with investments in mainframes and UNIX servers. NAS was often acquired by organizations with investments in Intel servers and with data stored using the Network File System (NFS). NAS also provided a way to easily share data between UNIX and Windows workstations.
SAN and NAS Technology
In support of describing the advantages and shortcomings of the two technologies, we need to define their technical characteristics. The data transmission technology of NAS is TCP/IP over Ethernet while SAN uses Fibre Channel. NAS uses a file approach to data transmission while SAN uses a block approach. The protocol of NAS is NFS while SAN uses encapsulated SCSI.
SAN and NAS Benefits
SAN advantages include enhanced data management, high performance through the block approach to data transmission and scalability in smaller increments.
NAS advantages include easy file serving, simplicity of management and scalability in quite large increments.
Both technologies offer a high-speed approach to backup that does not require local area network resources.
As to shortcomings, NAS owners are concerned about the limits in scalability, availability and functionality of their NAS solutions. Some SAN owners are concerned about implementation complexity and the lack of interoperability among the components of different SAN suppliers.
SAN and NAS Developments
As a result of mergers and data center consolidation, many organizations operate both NAS and SAN in their computing infrastructures. Having both technologies, while offering all the advantages, also tends to create operational complexity.
To address the shortcomings and to maximize the strengths of both technologies, some storage vendors have begun to offer a hybrid solution. Such a storage configuration uses a SAN on the back end with NAS on the front end. Most industry observers suggest that the ultimate goal of seamless interoperability and data sharing can and will be reached.
If your organization is just starting to think about implementing NAS or SAN, a hybrid solution should receive serious consideration. If your requirement is truly just shared file access, then a NAS will be most suitable. If shared access to databases, perhaps with failover, is your requirement, then a SAN is the better choice.