Hands-on with the OWC Mercury Elite-AL Pro Dual mini SSD

When I think of RAID, I usually envision a large box full of whirring drives installed in a rack, not a quiet little box that I can connect to a MacBook. Thanks to Other World Computing, the way I visualize RAID will have to change.

For those of you who might be unfamiliar with the term RAID, it stands for Redundant Array of Inexpensive Drives. In this review, I'll talk about RAID 0, which stores information on two or more drives that are linked together. RAID 0 is usually a much faster storage solution than just a single hard drive. RAID 1, on the other hand, just mirrors data written to one of the drives onto a second drive. It's great for creating a fairly bulletproof storage solution.

The Mercury Elite-AL Pro Dual mini (referred to as the Pro Dual mini from here on out) is a new product from OWC that is a fast, redundant quad-interface (USB/FW400/FW800/eSATA) dual SSD array (that's two solid state hard drives networked up together). When the Pro Dual mini is connected to a Mac through FireWire, no external AC adapter is required, making this drive an excellent portable RAID solution. The USB interface requires an optional AC adapter, adding both cost ($10) and weight to the equation. For use with eSATA, either a FW800 to 12-volt power cable (included) or the AC adapter is required to power the drive.

Physically, the Pro Dual mini fits two 2.5" SATA SSD drives into a tough 5.6 x 6.1 x 1.1 inch aluminum enclosure. The drives are OWC's Mercury Extreme Pro RE SSDs, which are rated at up to 263.6 MB/sec write speeds and 271.5 MB/sec reads. What would you use a small, fast RAID array for? A/V, digital photography, professional music or graphics are the use cases that come to mind.


The review drive came in with two 100 GB drives set up in a striped RAID 0 configuration for speed. The Pro Dual mini can also be set up in mirrored RAID 1 setup for reliability. Since the Core i7 iMac that was used for testing has no eSATA port, FireWire 800 was used for testing. The drive is pre-formatted for use with Mac OS X, using the standard Mac OS Extended (Journaled) format.

Pricing on the SSD models is what you'd expect for SSD-based RAID -- quite expensive. This device, with 200 GB of usable capacity, sells for US$600. A range of models is available from $180 for a 640 GB (RAID 0) device using traditional hard disk drives to $3199 for an 800 GB (RAID 0) SSD model. The best bang for the buck comes from the 2 TB HD version, which sells for $320.

With the Mac-friendliness of OWC products, the drive was ready to go out of the box. I plugged one end of the FW800 cable into the back of the drive, the other into the test iMac, and switched the drive on. There are twin LEDs visible through the cooling grill on the front of the drive, and they flashed red and blue alternately to indicate that the drive was being mounted. During operation, the red LED is used to indicate a drive failure.

The drive comes with a disk image of shareware software loaded on it, taking up 1.73 GB of space. Far more useful is the OWC Software Bundle CD, which includes Carbon Copy Cloner from Bombich Software (a TUAW favorite), Intech Software's SpeedTools Utilities, ProSoft DataBackup 3, and NovaStor's NovaBackup.

As you'd expect from an SSD-based RAID, the Pro Dual mini is completely silent in use, and it felt barely warm to the touch. A quick measurement with a thermocouple-based electronic thermometer showed the drive surface at 72.7°F in a room with an ambient temperature of 69.1°F.

How did it work in real-life conditions? I took the 1.73 GB shareware disk image and performed some read / write timings -- these aren't exactly official, but they do show the relative speed of the Pro Dual mini compared to another RAID array I own. That array is a DroboPro that is connected to the test iMac via an iSCSI connection over gigabit Ethernet.

I was able to read the file from the Pro Dual mini in 20.7 seconds, and write the identical file back to the device in 26.3 seconds. For the DroboPro, the times were 21.3 seconds for the read and 34.4 seconds for the write. I also duplicated the file on both devices and timed that operation; on the Pro Dual mini, it took 46.6 seconds, while the DroboPro was noticeably slower at 65.2 seconds.

To give a relative comparison of the speed of the device compared to the built-in drive in my iMac and the DroboPro, I also ran the venerable Xbench disk benchmarks on the three devices. The results of those tests showed the performance of the Pro Dual mini to be head and shoulders over the DroboPro and even faster than the built-in 7200 RPM HD in the iMac. Compared to the built-in HD, the Pro Dual mini was somewhat slower in sequential read / write speeds, but considerably faster in random read / write operation. The results of those tests are included in the gallery for your reading enjoyment.

My recent experiences with the SSD in my MacBook Air have made me a fan of the non-mechanical drives, and this test of the OWC Mercury Elite-AL Pro Dual mini SSD made me even more enthusiastic. The drive is faster in regular usage, it's completely silent (the rumbling of my DroboPro sometimes drives me nuts), and it's not going to turn a lot of electricity into heat. As with all SSD-based devices, the price on the OWC product should drop as the technology improves and manufacturing ramps up.

If I have one complaint about the drive, it's that the power switch slider is too small and requires a good push to turn on and off. A larger recessed on / off switch would have been just a few cents more expensive and would make the the Pro Dual mini just about perfect.

Update: The tech team at OWC responded to the above comments about the power switch, noting that "It is actually a "smart" power switch; there is no need to turn solution off ... just leave the power switch on, and the solution will power down and sleep when no disk activity occurs." They also noted that the power switch was deliberately made small in order to prevent the drive from being turned off accidentally.