What is a SAN?

 

A storage-area network (SAN) is a dedicated network that connects all the servers and clients to a shared pool of storage. The pool consists of servers, external storage devices, hubs and switches, and network and storage management tools.

SANS increase the availability of data by letting any server on the network access any storage device on the SAN. Server performance is also increased as storage-intensive processes such as backup and recovery are off-loaded to the SAN. SANs also promise lower cost-of –ownership through centralized management.

In recent years several technical developments have resulted in a bigger than ever need for extremely fast data links. We have high performance computers that have spawned increasingly data-intensive and high-speed networking applications, such as multimedia. However, the existing network interconnects between computers and I/O devices have been unable to run at the speeds needed.

The Gigabit-speed Fibre Channel has emerged as a response to that need. It is the transport protocol of choice for SANs. It is a high-speed transfer interface that can be used to access disk and tape storage devices that are attached to multiple hosts.

Most SANs today are a propriety solution because too many vendors have their own way of interpreting the Fibre Channel standard, so incompatibility among devices remains a major problem if you build your own. The three largest vendors are Compaq, IBM and EMC.

Industry analysts forecast that SAN technology will increase the level of centralized data storage and help solve storage-related problems across the enterprise. SANs will open the market to a couple of outsourcing options. Some corporations will begin locating all their storage at one central facility where it can be accessed by their geographically-dispersed divisions. There will also be new companies formed that do nothing but establish data bunkers and sell clients access just to the storage capacities that they need.

 

 

COMPARING TRADITIONAL STORAGE WITH SANS

 

ARCHITECTURE TRADITIONAL SANS BENEFIT OF SANS
Connection SCSI, Escon Fibre Channel Improves throughput 2.5 times to 100G bytes
Location Servers and storage must be co-located Servers and storage can be separated up to 6.2 miles(10km) Enables centralized administration and disaster recovery
Storage Device Dedicated to a server Shared among servers Improves resource utilization
Storage Management Platform by platform Across platforms Lower cost and better scale
Server/Storage Relationship Storage requests consume server cycles Minimal server involvement Server performance unaffected by storage tasks

 

Monique Emmanuel

Source for industry news is:

http://www.computerworld.com/home/print.nsf/all/990222914A

Additional resources are:

http://www.informationweek.com/722/san.htm

http://www.infoworld.com/cgi-bin/displayShow.pl?980616.ecostorage.htm

http://www.cern.ch/HSI/fcs/spec/overview.htm