If you want a Thunderbolt storage device that can house four 2.5-inch internal drives, there are now two options, the recently reviewed Drobo Mini and Promise Technology's Pegasus J4. The choice is easy, however, since the two are quite different from each other.
While the Drobo Mini's drive-bay design is great, the Promise J4 requires you to open its chassis to install and replace its storage drives. On the other hand, the J4 provides better performance and is more affordable.
Still, lacking RAID 5, the J4 is definitely not an ideal four-bay storage solution. It doesn't come with the much-needed Thunderbolt cable, either. But, priced at $400 (no storage included) or $800 with 2TB, the J4 makes a decent investment. If you don't mind bulkier storage devices, check out these alternatives for faster performance, larger capacity, and possibly lower prices.
Design and features
The Promise J4 is about the size of a Mac Mini, and you have to undo five screws on the bottom and lift up the top part of its chassis to get to its internal drive bays. Here, in order to install or remove drives, you need to use the screwdriver again, since each drive is secured to the chassis by another screw. Taking off the top is quite easy, and installing all four drives takes just a few minutes, but still, this is a backward design. The only good thing is that you can't accidentally remove a drive, which might lead to data loss. Promise says it's contemplating a better design for the next version of the J4.
With an aluminum and plastic body, the J4 looks good. There's an array of small LED lights on the front that shows the device's status. On the back are two Thunderbolt ports, the power connector, and a power button. You need to press and hold this button for a few seconds to turn the drive off. Most of the time, turning it off is unnecessary since the device's power status is linked to that of the Mac it's connected to: it goes to sleep when the computer is in sleep mode and wakes up when the computer is awakened and so on.
On the bottom, the J4 has a user-replaceable ventilation fan. This fan is quiet, and the J4 emits almost no sound and very little heat during operation.
Despite the difference in physical size and the number of drive bays, the Pegasus J4 is the next step up from the tiny Promise J2, and is not comparable to the four-bay Pegasus R4. This is because the R4 (like the R6) is a hardware RAID storage system, while the J devices are JBOD storage systems. This means the J4 can only provide software RAID configurations that the operating system natively supports. Since the J4 works only with Macs, it offers three hard-drive configuration options: RAID 0, RAID 1, and JBOD. (To find out more about different ways to set up internal drives, check out this post.)
Generally, it's overkill to use all four drives in a RAID 1, and extremely risky in a RAID 0. You can and should set up the J4 in two separate RAID 1 or RAID 0 volumes. In fact, the best use of the J4 might be setting up two of its drives in a RAID 0 volume to store frequently accessed data and the other two in a RAID 1 volume to store important data. This is similar to using two dual-bay Thunderbolt storage devices at the same time.
The JBOD setup option, called Concatenated Disk Set in Mac OS' Disk Utility, combines all drives into one volume, but it offers no RAID-related benefits, such as improved performance or redundancy.
Promise says that when a version of the J4 becomes available for Windows computers in the future, it will offer RAID 5. For now, the J4 works only with Mac OS X 10.6.8 or later. You can daisy-chain up to six J4 units together, to increase storage space or provide backups.
Apart from installing the internal drives, which is only necessary if you get the diskless version of the J4, setting up the device involves installing its software driver from an included CD (or you can download it from Promise's Web site). After that you need to use Disk Utility to configure the internal drives, which took just a few minutes in my trials.
Our review unit came with four Toshiba 500GB internal drives, model MQ01ABD050. These are regular laptop drives that spin at 5,400rpm. You can, however, use faster drives that spin at 7,200rpm, or even solid-state drives (SSDs). (See the compatibility list.)