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The performance crunch
As I pointed out back in 2004, the issue with these dense drives is performance. As every database or storage engineer will tell you, "High performance comes from lots of spindles." The more disk mechanisms you can access, the higher your overall performance will be, so these massive drives will hurt performance. While denser media speeds access, this capacity still has to squeeze through one narrow pipe (the drive's interface) and there's still only a single arm sweeping the heads over the platters. This is an important point because we're already seeing 500GB drives offered in enterprise arrays.
The answer to this problem is to use smaller drives. Array vendors have long since switched to 3.5-inch drive mechanisms, and the next big jump will be to 2.5-inch so-called "laptop drives." Seagate offers its Savvio family of 2.5-inch enterprise-class drives, while Hitachi and Samsung are targeting the enterprise with their little disks. These mini drives consume about half the power on a per-gigabyte basis as their larger brethren, and thus produce approximately half the heat as well.
But their biggest win is in terms of weight. It takes approximately 22 pounds of 73GB 3.5-inch disk drives to make up a terabyte of capacity. Swap these 3.5-inch mechanisms out for 2.5-inch units and you're down to about 6.5 pounds. Today's enterprise arrays typically pack about 250 drives into each cabinet, or more than 400 pounds of disk drives! Indeed, the drive mechanisms themselves make up more than half of the weight of a full enterprise storage unit. If we used 2.5-inch mechanisms, we would have closer to 115 pounds of drives--the disks shrink to approximately 25% of the storage device's total weight.
This was first published in June 2006