• What is Storage Area Network (SAN)?.
• SAN Advantages
• SAN Disadvantages
• SAN Virtualization
• Summary

A SAN is a collection of storage and backup devices connected together through a network that is totally separated from other servers via a switch. Fibre channel is the high-speed technology and communications protocol to connect those storage and backup devices. Fibre channel cables can be of several kilometers and its first 20 meters can be copper wire and if its length is more, then  fiber optical can be used.

A typical SAN consists of a farm of disk arrays, CD-ROM, tape libraries, etc. interconnected with Fibre channel and connected to the outside world through a Fibre channel switch or bridge. The connections inside the boxes can be Fibre channel, SCSI, ATA  or any other technology. Connecting all the storage devices into a network needs a plethora of hubs, bridges, routers, multiplexors, copper to optical converters, and other relevant devices as we do for a normal communications network.

1. SAN Architecture facilitates scalability - Any number of storage devices can be added to store hundreds of terabytes.

 
2. SAN reduces down time - We can upgrade our SAN, replace defective drives, backup our data without taking any servers offline. A well-configured SAN with mirroring and redundant servers can bring zero downtime.

 
3. Sharing SAN is possible - As SAN is not directly attached with any particular server or network, a SAN can be shared by all

 
4. SAN provides long distance connectivity - With Fibre channel capable of running upto 10 kilometers, we can keep our data in a remote, physically secure location.  Fibre channel switching also makes it very easy to establish private connections with other SANs for mirroring, backup, or maintenance.

 
5. SAN is truly versatile - A SAN can be single entity, a master grouping of several SANs and can include SANs in remote locations.

1. SANs are very expensive as Fibre channel technology tends to be pricier and maintenance requires a higher degree of skill

 
2. Leveraging of existing technology investments tends to be much difficult. Though SAN facilitates to make use of already existing legacy storage, lack of SAN-building skills has greatly diminished deployment of homegrown SANs. So currently pre-packaged SANs based on Fibre channel technology are being used among the enterprises.

 
3. Management of SAN systems has proved to be a real tough one due to various reasons. Also for some, having a SAN storage facility seems to be wasteful one.

 
4. Also, there are a few SAN product vendors due to its very high price and very few mega enterprises need SAN set up.

 

As it has been found quite complex, virtualization concept came into picture for the sake of effective and efficient management of SAN. Virtualization can be defined as an abstracted management of huge amounts of equipment and data. Virtualization takes all diverse and large complex storage devices and makes them appear as one Hugh volume.  Presently there are three proven methodologies for achieving SAN virtualization in the market.

•   Host-based virtualization - This methodology requires a control software program on every server that accesses the SAN. The main benefits out of this are easy installation and access. However, if the servers are loaded with different operating systems, then the control software has to support all of them. This mechanism seems to be highly beneficial under the situation in which there is a  need for incorporating NAS boxes to the network along with SAN.

 
•  Storage-based virtualization - It works in a homogeneous hardware environment, i.e., everything has to be from the same vendor. 

 
•  Network-based virtualization - This is the Vicom hardware method, which is in many pre-configured SANs. It is simply another component of the SAN that sits between the Fibre channel switch connected to the host servers and another Fibre channel switch connected to the SAN. The primary benefits out of this methodology is it can work even in a heterogeneous environment. That is, multiple servers running on different operating systems can access a heterogeneous SAN.

 

SAN is literally a separate network devoted entirely to storage. Almost all SANs communicate and connect to servers via a Fibre channel host adopter card and switch.