New Hybrid Drives Shift The Storage Picture

When I bought my Lenovo ThinkPad X201 a year ago, I had the option of getting a solid-state hard drive. Even though I was putting together the most tricked-out ThinkPad possible, I rejected it because of the cost per gigabyte. I don't remember the exact numbers, but there was a huge difference in price and the SSDs had only a fraction of the storage of a standard hard drive. Things haven't improved much. Today's ThinkPad comes with a 320GB 5400RPM drive; a 160GB SSD, half the size, costs $400 more.

Solid state drives (SSDs) offer an easy way to gain significant improvement in computing performance but at a price. Not only are they quite expensive, but there is a limit to the number of times you can reliably write to the flash memory in them, although it might be a large number of writes.

A new type of drive promises to make things more reasonable. On Tuesday Seagate announced the second generation of its solid state hybrid drives, the Seagate Momentus XT Solid State Hybrid Drive with the "FAST Factor advantage". These hybrid drives have some solid state memory on them--8GB of NAND memory, the type typically used in flash drives--but also a large 750GB conventional hard drive.

The 8GB of NAND is more than just a simple cache. Intelligent circuitry on the drive learns what your frequently-used files are and maintains them in the NAND cache. Data is moved to the cache when it is both frequently used and difficult to get to on the drive; this last part refers to fragmented files or files in locations typically inconvenient for the head locations. Once the learning process has had time to work, the NAND becomes a very large read cache; writes always go through to the hard drive. This means that writes on the NAND memory are conserved over time, preserving the effective life of the drive.

The result is a drive that performs nearly as well as a full SSD, but at a fraction of the cost per gigabyte. The MSRP for the 8GB/750GB model is $245. Some quick checks at Amazon find conventional Seagate 750GB drives at about $120 to $150, depending mostly on RPM. Intel SSDs run at $275 for 160GB, $545 for $300GB, and $1070 for 600GB. A standard hard drive might be half the cost, but with vastly inferior performance.

The performance is impressive, at least according to Seagate's tests. Tests typically show the hybrid drive performing close to an SSD and far faster than a conventional drive. Here are some examples in a video:

There are other advantages to the hybrid design; for example, if the flash memory goes bad, the drive can mark it out and work around it. But the real story is the cost per gigabyte of high performance. The latest hybrid drives might cost nearly twice as much as a conventional drive right now, but that disparity in price won't last long. The story of tech over the last few decades is that the price always goes down, down, down.

Yup, I wish one of these had been available when I bought my ThinkPad. I know when I buy my next computer, a hybrid SSD will be a feature I'll likely want. These look like a big deal in the making.