Promise Pegasus R6 review: Promise Pegasus R6

Promise Pegasus R6

Dong Ngo

Dong Ngo

SF Labs Manager, Editor / Reviews

CNET editor Dong Ngo has been involved with technology since 2000, starting with testing gadgets and writing code for CNET Labs' benchmarks. He now manages CNET San Francisco Labs, reviews 3D printers, networking/storage devices, and also writes about other topics from online security to new gadgets and how technology impacts the life of people around the world.

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7 min read

Apple and Intel announced the Thunderbolt variant of Intel's LightPeak interconnect technology this past February with emphasis on high throughput speed of particular benefit to storage devices. Promise Technology's Pegasus R6, the first Thunderbolt-enabled storage device on the market, for the most part delivers.


Promise Pegasus R6

The Good

The Thunderbolt-enabled <b>Promise Pegasus R6</b> offers superb throughput speed and a large amount of storage, and supports multiple RAID configurations. You can also daisy-chain the drive with up to five other Thunderbolt devices without decreasing the throughput.

The Bad

The Promise Pegasus R6 only works with Thunderbolt-equipped Macs for now, it's expensive and relatively noisy, and it doesn't include the necessary Thunderbolt cable or any other peripheral connections.

The Bottom Line

If you have a Thunderbolt-enabled computer, the Promise Pegasus R6's storage capacity, its features, and especially its performance are worth the hefty investment for those who demand fast external storage.

Effectively this is a Mac-only storage peripheral, as Apple's newer desktops and laptops are currently the only computers on the market with the necessary Thunderbolt port. The Pegasus R6 doesn't support other data standards like USB and FireWire out of the box, and given the prices of $1,500 for the 6TB version and $1,999 for the 12TB version, the R6 is a hefty investment. We expect that the price will come down as more Thunderbolt storage devices come to market, but if you need fast, high-capacity storage today, the Pegasus R6 is the fastest external RAID array currently available.

Drive type External Thunderbolt hard drive
Connector options Thunderbolt
Available capacities 6TB, 12TB
Product dimensions (LWH) 7.3x7.7x9.9 inches
Weight 22.2 lbs
Capacity of test unit 12TB
OSes supported Mac OS X 10.6.8 or later
Software included Pegasus utility

Design and features
The Pegasus is about the size you'd expect a storage device that hosts six 3.5-inch internal hard drives to be: it's very large. Nonetheless, like all devices made to work with Macs, the device manages to remain visually appealing, with an all-aluminum chassis. On the back, the R6 has a standard power connection port similar to that of a desktop computer, a big ventilation fan for the hard drives, another smaller vent for the built-in power supply, and two Thunderbolt ports. You can use one of these ports to connect the drive to the host computer using a Thunderbolt cable, which unfortunately is not included and costs another $49. With the other port, you can daisy-chain up to five other Thunderbolt devices, or a Mini DisplayPort monitor, without reducing the connection bandwidth, per the Thunderbolt standard. We connected two Pegasus R6 units together in our testing and they indeed suffered no drop-off in performance.

On the front of the R6, in addition to standard power button and status lights, you'll find the six drive bays. You can pull the drives out easily via small latches that are sturdy enough to prevent you from pulling a drive out accidentally. Once you remove a drive tray, you can install or replace a drive easily with a standard Phillips-head screwdriver. Our review units each came with six 2TB SATA 3 (6Gbps) hard drives. These drives by default were set up in a RAID 5 configuration to offer 10GB of storage space, leaving 2TB for data redundancy.

RAID 5 is generally the recommended setup for a multiple-bay storage device to offer a balance of capacity, performance, and data integrity. Pegasus R6 also supports RAID 0, 1, 50, 6, 60, and 10. In our trials, the drive switched between RAID 5 and RAID 0 in less than a minute. This is a great bonus as most other RAID-enabled storage devices would take tens of hours to build a RAID 5 array from scratch. Note that if one of the hard drives in the RAID dies, the Pegasus R6 would take up to 9 hours to rebuild the RAID configuration with a replacement drive. The device will still work normally during this time, however, just at a slower speed.

There's nothing to setting up the Pegasus R6. Out of the box, the drive is preformatted in HFS+, and once connected to a computer via Thunderbolt, it's immediately available on your Mac, just like other external storage devices. Despite that easy setup, the drive comes with a well-illustrated Quick Start Guide that walks you through the setup process and explains how its components function.

The drive contains an installer package of the Promise Utility software that enables you to customize the drive by changing its RAID setups, monitoring hard-drive conditions, and so on.

We tested the Pegasus the way we test external storage devices: by copying large amounts of data from one place to another and measuring the device's throughput speed. While this method doesn't show the top theoretical bandwidth of the device, it replicates what you would get from the device in real-world daily usage.

As the R6 is the first Thunderbolt-based storage device, we benchmarked it with two sets of tests. In the first set, we compared its performance with that of internal drives, both traditional hard drives and solid-state drives (SSDs). In the second set, we stacked the Pegasus R6 up against other popular external devices that use USB 3.0, USB 2.0, FireWire, and eSATA connections.

Our test computer used with the Pegasus R6 was a brand-new 2011 MacBook Pro running OS X Lion, with a SATA 3 (6Gbps) SSD. Although Thunderbolt's ceiling throughput speed is a much higher 10Gbps (about 1.2GBps), the transfer rate will be limited to the notebook's internal drive speed.

For this reason, in the tests against internal drives, we let the Pegasus work with the least involvement of the MacBook Pro's hard drive as possible. First, we timed how fast the drive performed when copying data within itself, from one folder to another. This means the drive had to perform both reading and writing at the same time. In this test, the Pegasus R6 registered 192.53MBps and 228.06MBps in RAID 5 and RAID 0, respectively--about five times the speed of the fastest SATA 3 internal hard drives and about 170 percent the speed of a typical SSD. After that, since we had two R6 units available, we performed the second test in this category by copying data from one R6 to the other, so that one of the units was doing the reading while the other was doing the writing. In this test, the devices registered much faster throughput at 323.8MBps and 353.2MBps for RAID 5 and RAID 0, respectively. This is about three times the speed of even the fastest SATA 3 hard drives and, again, some 170 percent faster than a SATA 3 SSD.

The second set of tests measures the Pegasus R6's performance against more traditional external storage drives. For these tests we copied data directly from the MacBook Pro's internal SSD, which imposes a throughput bottleneck. These tests show what a typical user can expect from the Pegasus R6, since it replicates how most of us would use an external storage device. In RAID 5, the Pegasus scored 210.5MBps and 177.5MBps for write and read, respectively. When we configured the drive in RAID 0 it did better, with 212.5MBps writing and 184.9 reading. These scores are about twice those of USB 3.0 devices and six to ten times that of even the fastest USB 2.0 external drive.

All in all, though we weren't able to experience even half of Thunderbolt's full 800MBps throughput, the Pegasus R6 is by far the fastest storage device we've ever seen. To put this in perspective, the device can finish transferring 50GB of data (equivalent to two Blu-ray Discs worth of content or five compressed full 1080p HD movies) in somewhere between just 3 and 5 minutes. Or it can do the same with a full CD's worth of data (about 800MB) in about 4 seconds at most.

While we were totally blown away and impressed by the Pegasus R6's performance, the drive's level of noise and vibration bothered us somewhat. This is likely due to the fact that it has six high-speed internal drives inside that all spin at 7,200rpm. The device isn't noisy enough to be a problem when tucked away under a desk, although it would be a shame to hide a good-looking drive like this. However, if you kept it on your work desk you'd quickly notice and be bothered by the vibration and noise.

Data transfer: Thunderbolt vs. internal (in MBps)
(Longer bars indicate better performance)
Unit to unit  
Self-read and write  
Promise Pegasus R6 (RAID 0)
Promise Pegasus R6 (RAID 5)
Plextor PX-256M2S
OCZ Vertex 3
Crucial M4
OCZ Agility 3
Patriot Wildfire
WD VelociRaptor 600GB
Seagate Barracuda XT
WD VelociRaptor 300GB

Data transfer: Thunderbolt vs. external (in MBps)
(Longer bars indicate better performance)
Promise Pegasus R6 (RAID 0)
Promise Pegasus R6 (RAID 5)

Service and support
Promise Technology backs the Pegasus R6 with a two-year warranty for all parts except for the fan and power adapter, which are covered for only one year. This is a rather short time period for a storage device that costs almost $2,000. On Promise's Web site, there's scant support-related information about its Thunderbolt-based products.

We were really impressed by the Pegasus R6's unprecedentedly fast performance, but were let down by its price and especially its lack of support for other peripheral interfaces. While you wouldn't buy the expensive Pegasus R6 to use exclusively with an older Mac or a Windows system, the fact that you can't connect it to those systems at all without an adapter is an annoyance. That's a minor complaint considering the Pegasus R6's performance, though. For Thunderbolt Mac owners with the capacity and storage-speed requirements to justify such a large expense, this drive is a worthwhile investment.


Promise Pegasus R6

Score Breakdown

Design 7Features 6Performance 10Support 5
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