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Promise Pegasus J2 review: Finally, a RAID-enabled, superfast, supercompact Thunderbolt drive

The uniquely designed Pegasus J2 is perfect for deep-pocketed mobile users who want a compact, superfast, and RAID-enabled storage device.

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Dong Ngo
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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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5 min read

The Promise Pegasus J2 may not be the first portable Thunderbolt drive on the market, but it's still one of a kind.

Promise Pegasus J2 (256GB)
7.8

Promise Pegasus J2

The Good

The <b>Pegasus J2</b> portable Thunderbolt drive is very fast, optionally bus-powered, compact, and offers RAID configurations.

The Bad

The Pegasus J2 is expensive, doesn't include USB 3.0 or a Thunderbolt cable, and requires a power adapter to offer top speed.

The Bottom Line

Uniquely designed, the Pegasus J2 is perfect for deep-pocketed mobile users who want a compact, superfast, and RAID-enabled storage device, but not the rest.

Despite that it's more compact than any other Thunderbolt portable drive I've reviewed, the J2 manages to be a dual-volume drive, offering users the option of using it as a RAID 0 (default) or RAID 1 drive. On top of that, it uses two solid-state drives as its storage to provide fast data speeds, no matter in what type of RAID you want to configure it in.

The J2 is far from perfect, however. It lacks support for other connection types, such as USB, and it requires an external adapter to offer top performance. It's expensive, too, costing about $800 for 256GB or $1,500 for 512GB, and you have to spend another $50 or so for the much-needed Thunderbolt cable, which isn't included.

That said, if you want a portable drive that offers fast performance, portability, style, and data security, the Pegasus J2 is currently the only one that fits that bill. If you're willing to sacrifice the RAID capability, also check the Buffalo MiniStation Thunderbolt, or the LaCie Rugged Thunderbolt for much better pricing and flexibility.

Drive type External Thunderbolt hard drive
Connector options Thunderbolt
Available capacities 256GB, 512GB
Product dimensions (WLH)
2.91 inches x 4.33 inches x 0.81 inch
Weight 4.23 ounces
Capacity of test unit 256GB (SSD)
OSes supported Mac OS X 10.6.8 or later

Design and features
The Pegasus J2 is just slightly larger than a deck of playing cards, and is about as thick. One of the drive's ends is slightly thicker than the other; at the thicker end, you'll find a Thunderbolt port and a power port. The power port is covered by a rubber lid and is not needed to use the drive. Similar to the rest of the portable Thunderbolt drives I've reviewed, the J2 is bus-powered; you just need to plug it into a computer with a Thunderbolt cable.

Unlike the other drives, however, by design, the J2 only works at only some 30 percent of its data-rate capacity when bus-powered. If you want the drive to work at its best, you do need to plug in the included power adapter. According to Promise, the reason for this is because the Thunderbolt technology supplies only 10W per port, which is not enough juice for the J2's two internal drives to offer optimal performance. In my testing, there was indeed a huge difference in terms of the drive's performance between using it bus-powered and with the adapter (more on this below).

The drive's adapter can be used anywhere in the world since it supports AC input in the 100-to-240-volt range and comes with changeable prongs to fit any type of wall power outlets. If that's not travel-friendly enough, the J2's package also includes a nice leather carrying case.

The Pegasus J2 comes with more than you need in terms of power plugs while lacking the much-needed Thunderbolt cable.
The Pegasus J2 comes with more than you need in terms of power plugs while lacking the much-needed Thunderbolt cable. Dong Ngo/CNET

The fact the drive has just one Thunderbolt port means that it can only be used at the end of a daisy chain in case you want to use multiple Thunderbolt devices together. This is not a big deal, though, since all portable Thunderbolt drives I've reviewed come with just one port. The drive offers no USB or FireWire support; consequently it can only be used with Thunderbolt-ready computers and is a lot less flexible than USB 3.0/Thunderbolt drives, such as the LaCie Rugged Thunderbolt or the Buffalo Mini Station.

On the inside, the J2 comes with two micro solid-state drives (SSD), which explains how it manages to remain very compact. It would be much larger physically if it used two standard SSDs. While the compact design is welcome, the downside is that you won't be able to replace the J2's internal storage yourself, which slightly defeats the purpose of RAID 1, in case you want to use the drive in this data-safety-first configuration.

I reviewed the 256 version of the J2, and out of the box it's configured in RAID 0 to offer the best performance, and the full 256GB of storage space. The drive is preformatted in HFS+ for Mac; all you need to do is plug it in with a Thunderbolt cable of your own and you're ready to go. If you want to use it in RAID 1, which reduces its capacity to 128GB to offer redundancy for data safety, you'll need to use the Mac's built-in Disk Utility to configure and reformat it. This process took just a few seconds in my trials and will erase all existing data on the drive.

The J2 comes with no software and it can also be reformatted to use with Thunderbolt-enabled Windows computers.

Performance
The Pegasus J2 offered stellar performance when used with the included external power adapter. When used as a bus-powered drive, however, its performance took a big hit. And obviously, the drive is faster in RAID 0 then when used in RAID 1. Overall, however, no matter how you use it, it's still one of the fastest portable drives on the market.

I tested the drive thoroughly. First I used it with the power adapter, and in RAID 0 it offered 202MBps for writing and 181MBps for reading; both were about the top speed compared with its peers. In RAID 1, these numbers were lowered to 180MBps and 178MBps for writing and reading, respectively, which is still very fast.

When used as a bus-powered drive, however, its performance changed rather dramatically. In RAID 0, it now scored 84MBps for writing, about that of a USB 3.0 drive, and 153MBps for reading. In RAID 1, the writing speed was significantly lowered to just 31MBps, about the speed of a USB 2.0 drive; the reading speed, however, was still at 151MBps.

Overall, the J2 offered very good performance. I do wish, however, that it could offer its optimal performance even when used as a bus-powered drive. For now, you do need to choose between performance and portability. I did notice that the drive became rather hot in an extended operation, noticeably hotter than any other drive of the same type. While it wasn't hot enough to cause any problems and it worked perfectly throughout my testing, it did give me a little concern about the drive's rather short two-year warranty.

Thunderbolt external drive data-transfer scores (in MB/s)
(Longer bars indicate better performance)
Read  
Write  

Promise Pegasus R6 (RAID 5)
177.53 
210.5 

Pegasus J2 (RAID 0 - with power adapter)
180.8 
201.93 

LaCie Little Big Disk SSD
186.8 
184.71 

Pegasus J2 (RAID 1 - with power adapter)
178.43 
180.46 

Promise Pegasus R4 (RAID 5)
171.1 
150.47 

LaCie Rugged Thunderbolt
154.9 
150.07 

Elgato Thunderbolt SSD
168.97 
120.61 

Reference eSATA drive
110 
99 

Reference USB 3.0 drive
105 
88 

Pegasus J2 (RAID 0 - bus-powered)
153.32 
83.83 

Pegasus J2 (RAID 1 - bus-powered)
151.67 
31.1 

Reference USB 2.0 drive
31 
30 

Reference FireWire 400 drive
45 
21 

Conclusions
Supercompact, fast, and supporting RAIDs, the Pegasus J2 makes a very good investment for Thunderbolt-enabled Mac owners who can afford it. The fact that it lacks USB 3.0, requires the power adapter for top performance, and is pricey will likely steer many general users away.

Promise Pegasus J2 (256GB)
7.8

Promise Pegasus J2

Score Breakdown

Setup 9Features 7Performance 8Support 8
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