Storage Area Networks PART 1

Storage Area Network (SAN) is a high-speed subnetwork of shared storage devices. A storage device is a machine that contains nothing but a disk or disks for storing data. A typical SAN consists of a farm of disk arrays, CD-ROM, tape libraries, etc. interconnected with Fiber channel and connected to the outside world through a Fiber 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, multiplexers, copper to optical converters, and other relevant devices as we do for a normal communications network

SANs originated to overcome the problems with network attached storage (NAS) devices, which - like ordinary servers - are difficult to manage and difficult to expand the capacity on. NAS devices also add to the traffic on the network and suffer from the delays introduced by the operating systems' network stacks. A SAN's architecture works in a way that makes all storage devices available to all servers on a LAN or WAN. As more storage devices are added to a SAN, they too will be accessible from any server in the larger network. In this case, the server merely acts as a pathway between the end user and the stored data.

A SAN is made up of a number of fabric switches connected in a network. The most common form of SAN uses the Fibre Channel fabric protocol (with Fibre Channel switches). Alternatively ISCSI could be used with IP switches. Connected to the SAN will be one or more Disk array controllers and one or more servers. The SAN allows the storage space on the hard disks in the Disk array controllers to be shared amongst the servers.

Few SAN Solution Providers

• McDATA - providing SAN solutions.
• Storage Area Network (SAN) Test Solutions
• SAN software and hardware solutions
• SAN Appliances provider
• Storage Area Network Appliance from Stonefly
• SAN Solutions by Rorke
• SAN Solutions by Dot Hill
• SAN Consulting Services
• SAN solutions for data intensive, enterprise applications.
• Tivoli Storage Area Networks (SAN) Solutions
• SOFTEK - Storage Management Software - Storage Area Network (SAN) Solutions
• Brocade develops Storage Area Network (SAN) infrastructure solutions that simplify the deployment and management of SANs
• SAN Solutions from Sun
• Simple, Safe, and Scalable SAN management solution
• HCL Technologies - Storage Area Networks (SAN) - Solutions and Services
• SAN Solutions by Legato
• AT&T
• HP Storage Works
• DELL EMC

SAN Advantages

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.

SAN Disadvantages

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.

Some Storage Technologies

• Content Addressed Storage (CAS)
• Fibre Channel
• Teradata
• Hierarchical Storage Management (HSM)
• Internet Small Computer Systems Interface (iSCSI)
• IP-based Storage
• Network Attached Storage (NAS)
• Optical Storage Technology
• Storage Area Network (SAN) 
• Redundant Array of Inexpensive Disks (RAID)