The race to ship a 500 GB mobile hard disk drive unit was heated last year. Hitachi was first to announce a fat 12.5 mm drive in January, but Samsung and Western Digital fought a pitched battle through the second half of the year to produce serious volume in a the slim 9.5 mm 2-platter form factor. 320 GB and 500 GB became common in the first half of 2009, with vendors adding a baby-step 400 GB size as well.
Until this month, all four major disk vendors have remained silent on the step past the half-terabyte barrier, however. Certainly any could have slapped together a 640 GB, 750 GB, or even 1 TB 4-platter semi-mobile disk drive using existing technology, as Hitachi did last year, but no such announcement came. But the break just came: Seagate has quietly added a 640 GB model to their 2.5 inch FreeAgent Go portable disk drive line. There was no press release, but this is a major step forward.
The rest of the Seagate FreeAgent Go line uses the modern 2-platter Momentus 5400.6 disk mechanism, so we can assume that a new member of that family will also be introduced shortly. The line today consists of two platter densities:
- The 160 GB ST9160314AS uses a single two-sided 160 GB platter
- The 120 GB, 250 GB, 320 GB, and 500 GB drives all use a 250 GB platter. The smaller units (named ST9xxx315AS) use a single platter, while the larger ones (ST9xxx325AS) use two.
Seagate could produce a 640 GB drive with three 250 GB platters, but it is difficult to cram three platters into a 9.5 mm case. Therefore, it is likely that Seagate will be introducing a new 320 GB 2.5 inch platter. If this is true, we can guess that the new drive will be named ST9640326AS. An inexpensive single-platter 320 GB ST9320316AS might soon be introduced as well, effectively ending the reign of the 250 GB drive as the budget portable capacity king.
With Seagate first off the dime, expect similar introductions by Western Digital, Hitachi, and Samsung in the next few months. 2.5 inch hard disk prices have fallen slowly for the last six months, but the second half of the year should see each capacity level replace the one below it at the same price.