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4 Gb Fibre Channel arrives -- but do you need it?

In the past 12 months, nearly every SAN manufacturer has announced or introduced 4 Gb SAN components. But the move to 4 Gb SANs may be more a product of vendor push than user pull.

SAN vendors are busy rolling out 4 Gb/sec Fibre Channel equipment. In the past 12 months, nearly every SAN manufacturer...

has announced or introduced 4 Gb SAN components, from host bus adapters (HBAs) to switches to directors. It seems that 4 Gb SANs have finally arrived.

However, just because something is available doesn't mean it's necessary. Unlike the move from 1 Gb SANs to 2 Gb SANs, the move to 4 Gb SANs may be more a product of vendor push than user pull.

The fact is that very few SANs are limited by the speed of the connections. A typical enterprise SAN is much more likely to be constrained by port limitations, considerations of topology and architecture and management issues than by raw speed.

At most enterprises, probably the biggest argument for a 4 Gb SAN is that it can't hurt. Unlike 10 Gb equipment, which is going to be expensive and not backward-compatible, 4 Gb switches, HBAs and other equipment are fully compatible with existing 2 Gb SANs. Therefore, in most cases, 4 Gb equipment can be installed in existing 2 Gb SANs with no problem. The SAN will continue to run at 2 Gb/sec but there will probably be some gains in reliability. Furthermore, there isn't much difference in price between 2 Gb and 4 Gb components and, over the next year or two, we can expect to see the price of 4 Gb equipment drop to the current price of 2 Gb components.

So, if that's the case, why are the manufacturers pushing so hard to introduce 4 Gb SANs? The reason may be competitive pressure. Vendors see 4 Gb as the next step in the market and no one wants to be left behind, even if it means getting out in front of their customers.

History demonstrates that enterprises will find a way to take advantage of any increases in speed and capacity that vendors can provide. A few years down the road, we'll all probably be wondering how we lived with SANs that were only 2 Gb. But, for the moment, storage administrators should consider carefully before jumping to 4 Gb.


Rick Cook has been writing about mass storage since the days when the term meant an 80 K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last 20 years he has been a freelance writer specializing in issues related to storage and storage management.

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This was last published in February 2006

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