It's one of those inevitable events that still sounds incredible when you finally hear it for real: Seagate announced yesterday it's preparing to deliver 1 terabyte (TB) consumer-grade internal hard drives during the third quarter of this year.

But at a $400 price point, the introduction may not actually have that big an impact on the hard drive market, where prices were said to have bottomed out last year, though they've been melting down steadily ever since. Today, 500 GB models average around the $100 mark, and Seagate's existing highest-capacity 750 GB Barracudas are selling at about $225. A suggested retail price of $400 will mean you'll probably see terabyte drives at $350 on the street before the end of the year.

So what would you get by investing in one 1 TB drive that you wouldn't get from two 500 GB models? To borrow a phrase again from Arlo Guthrie, is one big pile better than two little ones?

The answer to that, from Seagate yesterday, lies in the power savings: "a best-in-class 55% reduction in watts-per-gigabyte." File that under "D" for "Duh," since you're using one fewer drive per terabyte. Is there a performance gain to be realized? Seagate argues yes, citing a 105 MB/sec sustained transfer rate. That will be interesting to see, if they can actually pull it off. In recent Tom's Hardware tests, the 750 GB Barracuda ES managed a maximum (peak) transfer rate of 76 GB/sec MB/sec.

The problem with high-capacity drives in high-utilization settings is that performance doesn't always keep up. Transfer rates are mediocre, though certainly not as slow as bargain drives. It's access time that's the killer: Right now, both Seagate's and Western Digital's high-capacity drives are testing at 13 ms random access time, as opposed to 8 ms for smaller capacity drives. Seagate doesn't say much about access times for the ES.2.

That fact has led many system builders to suggest purchasing high-capacity drives such as Barracuda ES for media and file storage only, not for the operating system. In other words, pick a smaller-capacity performance drive for C:, and a big capacity drive for D:. That might not reduce your power consumption much, but you'll see the difference when virtual memory has to page out to disk.

One new feature Seagate is rolling out with the ES.2 is called Rotational Vibration Feed Forward (RVFF), the US patent for which remains in the application stage. As Seagate's application explains, the ES.2's new servo motor receives error information from its actuation arm, which helps it determine whether it's accelerating on account of forces other than its own making: for instance, being picked up while turned on. The analyzer can then study the error signal and create a kind of attenuator signal. It doesn't move the actuator arm back to compensate; instead, it adjusts the signal coming from the drive, almost like noise cancellation, to re-acquire a quality of signal similar to that of a hard drive at rest.

If it's RVFF that's responsible for boosting the ES.2's transfer rate (assuming those estimates are borne out in independent tests), then there could be a lot more peripheral motion in hard drive mechanisms than was originally thought. Seagate states it hopes RVFF will improve the error rates for its Barracudas by a factor of ten.