OK, I upgraded to unRAID 6 and added a couple more hard drives, as I was full before the upgrade.  (managed to get 14 HD's in a mid-tower case - 6 in 2, 3-in-2 5 1/4" bays & re-drilled the internal 3 1/2 rails to hold 8 more, instead of 6).  Hadn't even started transitioning from RFS to XFS yet, but v.6 was working. However the programs I ran in v.5 as plug-ins (Plex, SAB, CP, SB/Sonnar) seemed to be much slower in v.6 [whether I ran as plug-ins or in a docker] so I decided to do a complete system  shut down.  Bad idea, as I can't get it to re-boot now.  I thought it was the PS, so I got a new one, and no joy.  It turns on for 1-2 seconds, then automatically shuts down.  However I did discover that if I unplug the ATX 4-pin 12V CPU power connector, that it will not  automatically shut down (but with no power to the CPU it won't boot either).  So I figure it's either a bad CPU or a bad MB.

 

Meanwhile I found a 16 Bay 4U Rack-Mount File Server on CL. Just got it home, and wondered if I plug the v.6 USB key into this box, will my former unRAID configuration still work (assuming I migrate the same drives over), or is  my unRAID USB "keyed" not just to the USB flash drive, but also to the MB &/or SATA cards of my old computer.  I'd just rather migrate the whole thing, if that's what will be required rather than to move the drives, and then find out that I have to move the board too.  (Also if it IS a bad board, would I have a problem with a replacement - i.e. if the USB flash for v.6 is "keyed" to the MB is it to just a make and model, or is it to a specific board?)

key is tied to the hardware of the usb stick. Where it goes your license goes.

What he said.

 

You should be able to carry those drives and flash to any system, plug them in, make sure it's set to boot the flash, and boot, and see the exact unRAID system you are used to seeing.  unRAID is essentially hardware agnostic, and analyses the host system all over again each time it boots.  It loads all configuration information from the flash, and locates each drive by its serial number.  But it doesn't store anything about the host system, discovers it fresh at each boot.

Thanks. 

Hardware agnostic is good, and good to know.

Unfortunately the server I got is based on an ASUS A7V600 MB, which apparently does not support booting from a USB that isn't a zip or external CD, so I'm gonna have to get a new board. (Also the 3Ware Escalade 8 port SATA cards may not support more than 3 TB total per card (I need more like 25.5 TB per 8 port card supported.)