It's long been suggested that solid state drives represent the most important upgrade you can give a modern computer for boosting its overall performance. Today that remains true by a considerable margin, where even budget-oriented SSDs wipe the floor with the fastest 3.5" hard drives, providing users with nearly instantaneous access times compared to the 10ms-plus delay associated with faster 7200RPM HDDs.

Not only are SSDs faster than HDDs, but they also consume less power and generate less heat. Additionally, because they have no moving parts, they're quieter, more reliable and more compact than their spinning counterparts. These "bonus" attributes don't matter much to desktop users, but they're particularly advantageous to notebooks, which are increasingly outfitted with flash storage instead (or alongside) of sluggish HDDs.

Recognizing that demand, the Serial ATA International Organization standardized a new compact "mSATA" form factor in September 2009, letting manufacturers produce tiny 1.8" drives for ultrabooks and other such mobile systems. Despite the many advantages of SSDs, until recently, they were a costly option with a limited storage capacity, especially those of the mSATA form factor, which have typically been 128GB or smaller.

Therefore, we took notice when Crucial announced its m4 mSATA SSD in a 256GB capacity at under $1/GB. The mSATA drive is tiny compared to Crucial's standard 2.5" m4, and despite the size difference, both 256GB models feature the same read and write speeds of 500MB/s and 260MB/s -- an exciting prospect, indeed. Assuming there are no catches, Crucial's new mSATA offering could become the go-to solution for ultraportable upgrades...

Crucial m4 mSATA in Detail

Like the 2.5" m4, the mSATA version uses the Marvell 88SS9174 controller along with a large Micron 256MB cache to improve small write performance. Given that the Marvell 88SS9174 controller measures 17mm x 17mm alone, fitting it on a 30mm-wide PCB along with the 256MB cache and 256GB worth of NAND flash memory is an impressive achievement.

Crucial says its m4 series has a MTBF (Mean Time Between Failures) of 1.2 million hours, which is somewhat more conservative of an estimate than the ~1.5 million hours you'll find on most other SSDs. To accompany the usual MTBF figure, Crucial also provides a drive endurance rating for each model.

As mentioned, Crucial claims the m4 mSATA 256GB can achieve a read and write throughput of 500MB/s and 260MB/s, identical to the larger 2.5" model. The input/outputs per second (IOPS) rating is also the same, reaching 45,000 IOPS for 4K random read and 50,000 IOPS for 4K random write.

The 64GB m4 mSATA is supposedly good for 36TB of data, while the larger models have a rating of 72TB. That might not sound too impressive, but 72TB breaks down to an average of 40GB per day for five years, which is quite a bit for standard use. Besides, the m4 mSATA will be ancient history in five years anyway.

In terms of physical durability, Crucial claims that the m4 mSATA offers a shock resistance of 1500G and that's pretty typical among competing flash products. The company's new drives can also operate reliably at temperatures of up to 70 degrees Celsius and will survive 85 degrees when non-operational.

Like all SSDs, the m4 mSATA cites very low power consumption figures. At idle, all models use less than 100mW. When active, the 64GB and 128GB versions consume just 150mW, while the 256GB model has a rating of 160mW, which is still exceptionally low.

The m4 mSATA series measures 50.8 x 29.85 x 3.75mm and weighs 0.3 ounces (10 grams). The drives are compatible with both laptops and desktops, though you'll need an mSATA to SATA Adapter if you plan to install in a desktop that doesn't support an mSATA connector on the motherboard. They'll also work in RAID if you buy more than one.