Slash Storage Area Network Costs With I-SCSI


How can you gain the cost benefits of a storage area network (SAN) without a lot of unnecessary expense and Excedrin headaches?

Fibre channel, you say. After all, it's the most widely used way to connect devices and create a SAN. Besides, fibre channel provides a speed of up to 100 Mbytes per second. The not-so-good news is that fibre channel is expensive. Each port could cost as much as $1,000. What's more not all fibre channel devices can communicate with each other. You have to first hunt around and to find those fibre channel devices that can work with each other. To this end, testing the compatibility of devices has to rank high on your list of must do's before you go live.

Of course, if you had said I-SCSI as the answer the question, you probably the type whose thinking ahead of everyone else. I-SCSI uses warm and fuzzy TCP/IP networks to carry data. With I-SCSI, data transfers and SCSI commands get packaged (or encapsulated) inside IP packets. Instead of having to go through a lot of hassle and expense to put together a fibre channel network just for storage, with I-SCSI you can use the tried and true old network standby, Ethernet. Besides, you probably already have an Ethernet network installed in your data center. So, forget the fibre channel. Using SCSI commands sealed away in the IP packets lets you use existing storage management software with little modification. Great. You won't have to spend hours learning some new storage management mumbo jumbo.

By using I-SCSI, you'll get to save a lot of dollars on long distance links between pools of storage. Some of those exotic high availability strategies require data centers to be mirrored to locations several miles away. The cost of running a fibre channel connection over such a distance will make you think twice about the economics of doing this. On the other hand, I-SCSI enables you to use existing network connections without any modifications. You can use I-SCSI over short distances, too. Keep in mind, Ethernet technology is moving to gigabit Ethernet, which can support up to 125 Mbytes per second.

Of course, I-SCSI as great has it is does have one flaw, which isn't exactly fatal. The TCP/IP network turns out to be an inefficient way to carry data and SCSI commands. The design of a TCP/IP network calls for maximum redundancy over uncertain Internet connections. You can get around this limitation by putting fibre channel in the data center and I-SCSI over long distance links. This technique takes advantage of the best features of both network technologies, and lets you keep your options open as far as which technology to get tied too. Elizabeth M. Ferrarini - She is a free-lance writer from Boston, Massachusetts.


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