Perhaps someday mechanical hard drives will go completely out of style. We're not quite there yet, however, as HDDs still offer a high bang-for-buck in terms of raw storage space. And with NAND flash memory pricing being so volatile, it might be a long time before solid state drives reach pricing parity. Case in point, Amazon has on sale a 4TB Seagate Barracuda HDD (ST4000DM005) for $100.

That works out to two and half pennies per gigabyte. This isn't Seagate's performance model, though it does pair 64MB of cache with a SATA 6Gbps interface. According to Seagate, reads and writes average 161MB/s on this drive, while the maximum sustained data rate tops out at 190MB/s.

At 4TB, this is the highest capacity Barracuda in a 3.5-inch form factor. The same drive series in 2.5-inch form go up to 5TB, while the 3.5-inch Barracuda Pro goes all the way to 10TB.

The other difference between this and Pro models is the warranty—Seagate backs its Barracuda drives for 2 years and the Pro versions at 5 years.

Despite the shorter warranty, the price here is really good for a 4TB HDD. It even beats the price on a refurbished Western Digital 4TB Blue drive, which goes for $105 on Newegg.

You can grab the 4TB Seagate Barracuda here.