SANs create a dedicated network, focused on creating a universal any to any connectivity between storage and server nodes - a network that combines the best of mainframe bus and channel's high speed and data integrity benefits with networks' distance benefits, a network that frees the main LAN network from backup duties that consume valuable bandwidth, a network that is scalable allowing increments in capacity without disruptions while leveraging the existing investments in legacy platforms and existing data, a network that provides centralized control while providing remote data vaulting for disaster recovery, a network that offloads storage management tasks from application servers and speeds up the entire network, thus allowing users the benefit of fast data access. SANs will eventually be at the core of every enterprise's data center, allowing companies to design centrally-managed data centers that embrace and interconnect farflung global SANs and provide service to all of their servers, no matter how far or no matter what operating systems they are running on.

This new focus on data storage, as a key asset to manage, is obvious given the rise in dollars being spent on storage to the tune of 40-50% of total IT dollars in 1998. The rise in storage requirements, is being fueled by the birth of incessantly newer internet, data warehousing and ERP applications and further stoked by the lure of cheap disk drives at 5 cents per MB at the end-user level today.

Challenges/Caveats

One of the major shortcomings of NAS storage architecture is that the network on which NAS runs is also used for data access by clients to retrieve data from the file server or communicate with application servers. The data movement between the disk and tape servers also goes over the same LAN. This creates a major network bottleneck when the number of users increase. Further the overhead of network stack contributes to higher data latency during server or client to storage communications.

While NAS works well for documents, file manipulations and transaction based applications, it is not necessarily most advantageous for database applications because it is file-oriented. Also for high bandwidth video applications, NAS slows down since the shared network on NAS gets clogged fast with multiple large files and starts to become a bottleneck.

A SAN (Storage Area Network) is a dedicated high performance network to move data between heterogeneous servers and storage resources. Being a separate dedicated network it avoids any traffic conflict between clients and servers. A fibre channel based SAN combines the high performance of an I/O channel (IOPS and bandwidth) and the connectivity (distance) of a network.

Performance

SAN enables concurrent access of disk or tape arrays by two or more servers at high speeds across fibre channel, providing much enhanced system performance.

Availability

SAN has disaster tolerance built in since data can be mirrorred using FC SAN up to 10 km away.

Cost

Since SAN is an independent network, initial costs to set up the infrastructure would be higher but the potential exists for rapid cost erosion as SAN installed base increases.

Scalability

Scalability is natural to SAN architecture, depending on the SAN network management tools used.

Interoperability

Like a LAN/WAN it can use a variety of technologies such as serial SCSI, ESCON, FICON, SSA, ATM, SONET etc. This allows easy relocation of backup data, restore operations, file migration and data replication between heterogeneous environments.

Manageability

• Data centric
• Part of Server cluster
• Thin protocol for low latency
• DMA to server RAM - direct communication to Data

Future of SAN

• Embedded and Distributed File System
• Intelligent SAN-smart File System where portion of File System is in SAN
• Data routing
• Storage network management
• Concurrent processing and manipulation of intelligent data streams
• Server Independent Storage Tasks
• • Peer to Peer copying
  • Peer to Peer backup
  • Automatic back up using Fibre Channel
• Data Sharing, Data Formatting
• Security - Authorization, Authentication, Access Control

SAN technology, in the future, may also interconnect worldwide with other SAN intranet sites to provide instantaneous replication of corporate data to these remote sites to create a global information system. This would allow local access to fast while being up-to-date.

Challenges

As with all new technologies, SAN developments must rapidly happen in areas of data management, security features, interoperability test suites, availability of VI adapters to improve latency between interconnected servers and the availability of SCSI/Fibre Channel bridges.

Additional benefits of NAS for Web Servers accrue when using load balancing and web caching technologies.

The market for Storage Subsystems is concentrated in top 10 players. The top 3 players including Compaq (including DEC acquisition), IBM,and EMC alone control 50% of the market. Internal RAID is being led by Compaq, HP and Dell servers.

SAN fibre channel products are increasingly being introduced in the market including fibre-channel adapters, hubs, switches and routers, SCSI/FC bridges, disk drives and testers from multiple sources.

Eyeing the advantages and popularity of FC/SANs the leading data networking vendors like 3COM have jumped in to embrace the technology. Not far behind would be major players like CISCO, Lucent and Nortel/Bay Networks eyeing the convergence of voice and data networks and associated centralized database servers for interactive voice response and e-commerce applications for the global marketplace.