Adam and Eve rode dinosaurs to church?
Posted in Storage Interconnects & RAID, Advisor - Tom by Tom TreadwayJust this last Saturday on SNL’s Weekend Update, my primary source for news, they mentioned a poll where 66% of Americans think Bush is doing a poor job in Iraq, while the other 34% think Adam and Eve rode dinosaurs to church. (Oops. I think I just lost my red state readers – both of them. Oh, but it makes me laugh. 
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Anyway, the only reason I mentioned it is that Byte and Switch is conducting a poll on SAS with similarly bizarre results. Of course it’s not Byte and Switch’s fault. They just leave the steaming pile on the floor and let the readers step in it.
The first question in the poll is: “Is SAS a viable alternative to Fibre Channel as an enterprise-class drive?” And out of 85 responders so far, 37% said no! (Another 14% said “not sure”, but that’s an acceptable answer. It just means that MaryC needs to do more webinars for the uninitiated masses.)
Why are these people saying “no”? The question isn’t about FC as a SAN. It is about FC as a drive. And if you check out the Seagate enterprise drive website or the Hitachi enterprise drive website, two of the market leaders for FC drives, you’ll see that their FC, SAS and U320 drives are all identical, except for the physical interface. They use the same heads, same servos, same media, same motor, same case, same command interface (SCSI) – just a different interface chip. They’re the same dang drive!
Now I can see how some folks would have said U320 isn’t a replacement for FC. U320 is a cabling mess compared to FC, plus FC has dual ports for redundancy.
But SAS has a similar small cable, dual ports, and similar transfer speeds. A SAS drive can move data at 3Gb/s, while a FC drive can move data at 2 or 4Gb/s. Since the media on the fastest drives is still only ~1Gb/s, the interface speed is somewhat moot.
So what am I missing? Why did 37% say that SAS isn’t a viable alternative to FC? Pat, can I buy a clue?
TT