Deciphering NAS, SAN Storage Wars

IT must untangle today's enterprise-class technologies to get a handle on tomorrow's systems.

IT managers shopping for storage in todays market will find more options and vendors than ever before, but are there too many choices?In the enterprise-class storage networking world, a battle is already raging between NAS (network-attached storage) and SAN (storage area network) vendors. Things will get even more confused in the near future when companies such as Cisco Systems Inc. and IBM break into the market with iSCSI-based products.

Currently, NAS and SAN offerings appeal to different markets (NAS generally captures the low-end to midrange market; SANs are more often found in the high end). However, as NAS performance continues to improve, IT managers will have a harder time choosing which system is the best for their enterprise.

The SAN approach

Because SANs work almost like directly attached storage (RAID arrays appear as SCSI devices), they can provide high-performance storage for enterprise-class applications.

A typical SAN consists of Fibre Channel storage units (tape or RAID) that are networked to servers via Fibre Channel switches (from vendors including Gadzoox Networks Inc.)

The primary benefit of a SAN setup is its ability to provide device sharing, which allows storage resources to be consolidated. With a SAN in place, an IT manager can make single storage purchases instead of buying separate external storage units for each hardware platform.

A few weeks ago, Nishan Systems began shipping switches that have the ability to convert Fibre Channel traffic into Gigabit Ethernet traffic and vice versa. As Fibre Channel and networking vendors continue to grow, we should expect to see more hybrid systems like these in the future.

NAS components range from Quantum Corp.?s tiny 5GB Snap Servers to 12-terabyte-size units from Network Appliance Inc. For the low-end to midrange market, the chief attraction of NAS is that it is easy to implement-in eWeek Labs tests, weve gotten some NAS schemes up and running in less than 15 minutes.

Where NAS fits in

NAS communicates through the ubiquitous IP protocol (Ethernet and Gigabit Ethernet), so it doesn?t require expensive host bus adapters, which are required for Fibre Channel, and is thus a good solution for providing general-purpose storage services to low-end clients as well as high-performance servers.

The addition of Fibre Channel storage subsystems gives EMC Corp.?s and Network Appliance?s enterprise-class NAS systems high performance and scalability.

For the most part, enterprise-class NAS systems have been useful as content caching appliances for static content and streaming media, as well as some high-performance file serving. But high-end databases and server clusters primarily use SANs for their storage needs.

The major bottleneck in NAS products is the thin-server processing unit, which manages the file system and TCP/IP operations. Thin servers have highly optimized operating systems that are designed to deliver files as quickly as possible, but the software processes that sit between clients and their data introduce a large amount of latency compared with SAN systems.

However, the tables seem set to be turned with the emergence of startups such as BlueArc Corp. that aim to move software-based operations to hardware.

BlueArcs SiliconServer (which will be available later this spring) uses four customized processors to handle TCP/IP, protocol subsystem management, file system management and storage subsystem management. In early demonstrations, the SiliconServer has been a fast mover in basic storage benchmarks, but its viability in the enterprise storage market will have to be earned.