NAS has the edge as storage booms

Demand for network-attached storage has boomed thanks to the dotcoms. Nicholas Enticknap reports

Demand for network-attached storage has boomed thanks to the dotcoms. Nicholas Enticknap reports

Several major suppliers, including Compaq, Hewlett-Packard and Sun Microsystems, have announced network-attached storage (Nas) products in the past few months, and IBM is expected to join them shortly.

This enthusiasm for Nas over storage area networks (Sans) has come about because the implementation of Sans is complex and the technology is arguably immature. Nas is being sold as plug-and-go, so is in demand from the fastest-growing user sectors - dotcoms and application service providers.

Last year Gartner forecast that the Nas market would have revenues of $5.1bn (£3.5bn) by 2003. The analyst group has now revised this estimate to over $6.5bn.

Nas market leader Network Appliance doubled both sales and profits in its last financial year, even better than the year before when its growth was nonetheless 75%. EMC, which holds second place in the market with 30% market share to Network Appliance's 40%, says its Nas sales are running at 10 times the level of a year ago.

Massive market growth estimates have pushed some big names into the marketplace. Sun, which invented the Network File System (NFS) protocol in 1984, has realised that network file systems are a money-spinner, and launched its Stor Edge N8000 family in April. The N8000 offers capacities of up to 800Gbytes, but Sun promises to have a 10Tbytes system in the near future.

HP unveiled Nas versions of its XP256 and XP512 enterprise disc subsystems in June under the name Net Storage XP. Compaq followed in July with its Task Smart N-Series, which scales to 1Tbyte.

IBM is dropping strong hints that it will be entering the market soon. And EMC, which entered the market in 1996, announced enhancements to its Celerra range in both April (improved functionality) and July (a 60% increase in performance), while Network Appliance is planning a product launch for the end of this month.

Nas differs from Sans in several respects. Nas devices plug into an existing network; a San is an independent network in its own right. Nas devices use existing standards and protocols - typically Ethernet for device access, TCP/IP for data transfer, and CIFS and NFS for file sharing. Sans have their own set of standards.

A Nas device can thus be installed and in use very quickly. Sun claims that its N8200 filer can be installed in less than 10 minutes. Compaq claims its Task Smart Nas device can be configured in 30 minutes. Installing a San means, first, building the network infrastructure, and then ensuring all the components work with each other.

It helps that a Nas device is much more of a product than a system. Network Appliance UK managing director Tim Pitcher says, "We place our emphasis on appliances - a product that does one thing extremely well and is designed for that purpose."

He adds, "Instead of AIX we have a skinny microkernel focusing on data storage and on data management. A mobile phone has more code than we do."

Finally, a Nas device allows data sharing between Windows NT and Unix servers. A San provides for sharing of storage devices rather than data. Sun storage marketing manager Chris Atkins says, "Nas is the only thing that allows for heterogeneous storage of all types apart from the mainframe."

For all these reasons, sales of Nas devices are building up faster than sales of Sans but the two types of storage system are complementary rather than alternatives: they serve two different purposes.

Frederick Fabricius, IBM San manager, says, "If you have hundreds of servers with small files, transferring those files across TCP/IP is not such a big problem. But high speed transfer of data is not suitable in the Nas environment, because of the need for SCSI-to-IP conversion and because TCP/IP is poor for data transfer. If you have a few consolidated servers with high bulk volumes of data, clearly the advantage is with the San."

Nas v Sans the pros and cons

Network-attached Storage

  • Most devices can access files across a Lan or Wan

  • Data accessed by filename and byte offsets. Supports file locking and user authentication

  • Enables file sharing between different operating system environments

  • File system managed by head unit

  • Back-ups and mirroring are at file level and can be compressed using "snapshot" technologies.

    Storage Area Network

  • Only servers with Fibre Channel can connect. Maximum distance limited to 10 kilometres

  • Data addressed at disc block level

  • File sharing is dependent on the operating system and is not available in all environments

  • File system managed by servers

  • Back-ups and mirroring is at block level, even if the blocks are empty.

  • Read more on Networking hardware