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Hard disk drives vs. solid-state drives: Are SSDs finally worth the money?

September 17, 2012 06:25 AM ET

Using the Blackmagic Disk Speed Test, the WD Black showed a sequential read/write performance of 122.2 MB/sec. and 119.6MB/sec., respectively. Random (as in Random Access Memory, or RAM) performance is where the drive fell flat: the disk had a random write performance of 67.6 MB/sec and a random read performance of 34MB/sec.

Random performance is particularly important as the drive begins to fill with data and the read/write head must move across the spinning disk to locate the information you want. That requires more and more time as more data fills the drive.

Seagate's Momentus XT Solid State Hybrid Drive

There are industry analysts who believe the hybrid drive's time has come and gone. If you blinked, you missed it.

I respectfully disagree.

Hybrid drives can be a bridge between hard drives and SSDs. They offer SSD performance on critical operations such as boot up and application load times, and provide vastly higher capacities for the money than an SSD.

Fang Zhang, an analyst with IHS iSuppli, says most consumers purchasing a $700 PC or laptop aren't going to spend hundreds of dollars on an SSD. Hybrid drives, on the other hand, can be had for as little as 14 cents a gigabyte. For example, a 500GB Seagate Momentus XT can be purchased on Amazon for $69.99. The owner of that $700 laptop would be a lot more willing to spend one-tenth the price for a significant storage-performance upgrade, Zhang contends.

On the other hand, is that what consumers are most concerned with? In the immortal words of that Home Alone kid: I don't think so. I believe that the average consumer is more concerned with capacity than performance. And with a hybrid drive, you get both.

But while hybrids offer significant performance improvements over traditional hard drives, like hard drives, they have mechanics (moving parts). If you drop your laptop while it's powered up, there's a chance you'll damage the hard drive component of a hybrid drive. That's another factor to think about when deciding what type of drive to get.

Testing the hybrid

During its initial OS installation, the Momentus XT captures boot files and places them in a special segment of the NAND flash where they remain for the life of the drive. The feature ensures that the drive always boots from flash and not from the spinning disk.

Momentus XT
Seagates Momentus XT hybrid drive with the back cover removed

The drive also has an "Adaptive Memory" algorithm that monitors which applications and data are initially loaded into a system and then "learns" to place that data on the SSD to speed up performance. Over the course of three boot-ups, system performance becomes optimized to each user's preferences.

In my benchmark tests of the Momentus XT, the initial boot up took 20 seconds, the same as the WD Black hard drive. Then I rebooted -- and the Adaptive Memory firmware kicked in and began optimizing the drive for my system. The second boot took 15 seconds; by the third boot, the drive was down to 12 seconds -- very impressive.

Copying the 327 JPG images took 29 seconds. Opening a 300KB, 372-page Word document took 1 second and then an additional 57 seconds to download all 372 pages.

On the second try, opening the Word document took 1 second again, but all 372 pages loaded in only 15 seconds. By the third try, the cache had really kicked in and it loaded all 372 pages in 10 seconds.

When it came to using the Blackmagic benchmarking software, there was an obvious problem: The software shows only the Momentus XT's hard drive performance, and that doesn't really reflect the drive's true capabilities.

With that in mind: For sequential read/writes, the Momentus XT showed 106MB/sec. and 114MB/sec., respectively. On random read/writes, the drive came back with 99MB/sec. and 90MB/sec., respectively. Those results demonstrate that the SSD was not in use for these functions; these read/write speeds came from the spinning disk in the drive. And, while very respectable for a hard drive, the results come nowhere near SSDs' results, which are anywhere from 200GBs to 250GBs.



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