Q I rearranged the room in which my iMac and Promise Pegasus Thunderbolt RAID R4 live. Before doing anything, I checked that the RAID system was fully up to date, and shut it down using the supplied (and current) Promise Utility app. iMac and RAID were moved gently, reconnected, and powered up. To my horror, three of the four drives then showed red lights, indicating hardware failure. I shut everything down again, checked connections and reseated the drives in the RAID, powered it up, then the iMac. Now all four drives are ‘showing red’. Have I killed it?

A Hopefully not. Sometimes when you have shut a Promise Thunderbolt system down like this, the drives cannot be put back online automatically, and the system looks as if it has suddenly died. You have done the right things so far, but now need to open Terminal and force your RAID drives back online at the command line.

Thankfully this is not in the least scary. With the RAID unit running and properly connected, type the following command to start the interactive version of the Promise Utility:
promiseutil

The command prompt will change to cliib>, showing that you now have interactive control through the utility. Then type the following commands one after the other:
phydry -a online -p 1
phydry -a online -p 2
phydry -a online -p 3
phydry -a online -p 4

These will put the four drives back online one after the other. If you have the six-drive version, R6, you will need to add a couple of lines to handle its extra two drives,
phydry -a online -p 5
phydry -a online -p 6

Sadly you cannot convince an R4 that it has the extra drives!

The RAID lights should now become green, your world return to normal, and to express your relief you can send me an Amazon voucher (in my dreams). Quit promiseutil by typing
exit
which should return you to the normal command shell prompt. Close the window in Terminal, and quit it.

If not, you can try shutting everything down again, stripping your Thunderbolt daisy chain down to just your Mac and the RAID system, starting the drive up, then your Mac, and going straight into Terminal with the commands above. If you still cannot resurrect your RAID system, it is time to invoke its warranty, or contact Promise support.

Comments
It is extraordinary that the Promise Utility app is unable to do what a few simple commands in Terminal can, and must rank as a pretty serious bug. This command line tool is surprisingly powerful and does not appear to be properly documented in the manual. It is also malformed, as typing
man promiseutil
which is the standard way to view documentation in Terminal, does nothing. Instead to see its various sub-commands, you should type
promiseutil -h
or, at its cliib> prompt, the command
help
To get further details on an individual command, at its cliib> prompt type just the name of the command, with the -v option for full information.

Your Promise Pegasus R4 system should show a firmware version of 5.04.0000.36, with the Promise Utility at version 3.18.0000.36. Note though that there are two different releases with the same version number, one OS X 10.6 and 10.7, the other for 10.8 and later. Updates are at Promise support.