Promise Pegasus2 M4 review

Price when reviewed

Desktop RAID units don’t get much more compact than the Pegasus2 M4: it’s a chipper little block only 107mm high and 127mm wide, all dressed in black. It owes its diminutive size partly to its use of 2.5in hard drives instead of the 3.5in drives found in many RAID devices. These pop smoothly out of the chassis at a press of the button to the right of each drive and are mounted on sliding rails, making it easy to get them in and out to replace or upgrade.

Promise Pegasus2 M4 review

Promise Pegasus2 M4 - hero photography

The four drives supplied with our review model were 1TB, 5,400rpm Toshiba HDDs, but the drive screws are standard, so any four matched 2.5in drives should be fine. The only downside is that 2.5in drives don’t offer as much potential for future upgrades as 3.5in units, because 2.5in drives don’t reach the higher capacities.

In OS X, it’s easy to set the Pegasus2 to work. Simply plug in the mains lead – there’s no external power brick – then hook up one of the two Thunderbolt 2 ports and it connects. It’s supplied preformatted as a RAID5 configuration with HFS+, and you can rebuild the array using the supplied Promise Utility software.

With multiple screens and tabs to navigate and options spread throughout them, it could be easier to use, but it has some useful wizards to help you set up your RAID array for specific tasks.

Promise Pegasus2 M4 - front panel

In Windows, the news isn’t so good. For one thing, you need to install a driver before the M4 can be recognised; on our test Boot Camp partition, the driver crashed the system immediately after install or upon rebooting. The Windows version of the Utility software didn’t always behave as expected, either.

Eventually, we got the drive up and running by removing the drivers and physically removing two disks, before setting up a simple two-disk RAID with the remaining disks. After this, we were able to rebuild the array with four drives and resume testing.

Once set up, the Promise Utility software works well, with plenty of real-time monitoring and management features, plus some simple tools that let you make necessary repairs and see which drives are operating within the array.

Promise Pegasus2 M4 - rear view

Performance is beyond what you’ll get from any single-drive USB 3 or Thunderbolt 2 product but, with 5,400rpm disks, the Pegasus2 can’t match the speeds of the drives from OWC and CalDigit. It will hit sequential read speeds of 400MB/sec while reading or writing large files, but its rivals are consistently faster, particularly under Windows.

For some users, the M4’s compact size might make all the difference, especially since it offers an easy upgrade path to 2.5in SSDs. If performance is of greater importance than a small form factor, though, you would do better to look elsewhere.

 Promise Pegasus2 M4 specifications

Capacity 4TB
Maximum capacity 4TB
RAID support 0. 1, 5, 6, 10
Hot swappable? Yes
Cost per gigabyte 19p
Interface 2 x Thunderbolt 2
Power supply External
Spindle speed N/A
Size 127 x 167 x 107mm (WDH)
Buying information
Warranty 2yr RTB

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