Resurrection of a RAID drive
What would I need to get a second–hand Promise Pegasus R4 external RAID drive with two dead disks working with my 2017 MacBook Pro? If two of its four disks have already failed, you’d be best replacing the whole set before the others follow suit. RAID drives work best when all disks are e the same model, so their specs match. In the R4 this requires capacities of 1 to 4TB each.
Get models similar to those known to be compatible (see the manual from bit. ly/prmpr4pdf), such as more modern equivalents from HGST’s Deskstar series. If you can, and this isn’t always easy, source them so that they each come from a different manufacturing batch. This is because drives from the same batch tend to fail at about the same time, and the worst thing that can happen to your RAID is for two disks to die within a few hours or days of each other, as that’s near certain to lose your data.
Fit the disks to the sledges. You may need to replace their retaining bolts, which can be hard to extract cleanly. Get the Promise Utility from Promise’s Download Center ( bit.ly/prutil).
With an array of four disks, a popular choice of RAID level is 5, which is fault– tolerant and significantly faster than a single disk. You will, however, also need a Thunderbolt 3 to 2 adapter, which is able to work with Thunderbolt 1 as well. Connect the R4 to your Mac, power it on, open Promise Utility, update the R4’s firmware if needed, and run its configuration wizard. Finally, use Disk Utility to erase the array in Mac OS Extended (Journaled) format.