Thursday, 18 May 2006

The Case for 10Gb/s

Fibre channel storage speeds are now up to 10Gb/s as I'm sure we're all aware. Brocade, McDATA and Cisco all have 4Gb/s products. Question is, are they really necessary?

Pushing a full 1 or 2Gb/s of data across a fibre channel connection at a sustained rate requires some decent processing power, so why move things on to 4 and 10? Well, 4Gb/s and 10Gb/s certainly prove useful as ISL connections. They reduce the number of ports required and subsequently the cabling. But with faster connections comes a price; cabling distance for multimode fibre drops significantly. Check it out here :

So faster speeds yes, but shorter distances. Wasn't one of the benefits of fibre channel to remove us from the 25m SCSI cable restriction?

One other thing to bear in mind. If we start consolidating traffic into less but faster ISLs, I'd want to be very sure that the aggregation of traffic gives me adequate quality of service for each of the traffic types sharing the link. Cisco can do that; McDATA are talking about it; Brocade, not sure.

So what do I think, are the faster speeds necessary? Well, I can see the benefit of 4Gb/s for storage ports, less so for host ports. I can also see the limited benefit of using 10Gb/s for ISLs between locally placed switches, but I think that's where it ends for 4 & 10Gb/s. Hosts and storage systems can't push that degree of data around and switch backplanes can't move the data around either. So for me, 1/2Gb/s will be the norm, 4/10Gb/s will be for special occasions.

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