Help: Major problem installing a 2nd drive (SSD) in 2011 i5 Mac Mini

Question

I've installed an Intel 520 SSD in the second bay in my mum's 2011 Mac Mini. I used OWC's kit and the installation went well.
For two days now I have tried cloning over the OS from the HDD to the SSD but I can't get the computer to boot from the SSD. I cloned using both SuperDuper and CCC. Initially I had problems getting the cloning operation to complete but I suspect that was because I forgot to turn off Spotlight on the SSD before cloning.
Once I managed to clone the HDD (with SD), I can select the SSD under Sys Prefs - Startup Disk but the system won't boot from it. I notice this because after a reboot About this Mac reports that the HDD is the boot disk even though I selected the SSD. At the beginning of the boot, sometimes the apple symbol (on the grey) screen flickers a few times between the apple and the circle with a diagonal line through it, which I take to mean that the SSD isn't ok. Then the computer defaults to the HDD instead.
Also, if I click Option to get the boot menu on startup and select the SSD, I will only get a grey screen with the apple symbol and the spinner. I can leave this for ten minutes without the system booting fully.
I ran AHT (normal, not extended) but no problems are reported. Disk Utility reports no errors on the SSD.
Then I reset PRAM and suddenly the computer booted from the SSD. Hurrah I thought, but then, equally suddenly, it failed to do so, defaulting to the HDD.
Could it be that the Mini can only boot from one of the drive bays?
Or is my SSD faulty? - does Intel have a special diagnostics tool perhaps? I found this page about some bug between SF2281-based drives (like the 520) and an Nvidia chipset but I'm not sure that applies to the 2011 Mini.
I'm a bit at a loss here so would appreciate some help.
Thanks very much in advance
Philip

Answer 1

pullman wrote:
First -254 which happens right away. From googling a bit I've discovered this may have to do with having chosen the drive as opposed to the volume as source/target.
So selecting these (but being confused as to how the recovery partition could be included in the restore if I choose only the boot volume and not the boot drive) the restore began. However it stopped after a few minutes complaining about an "input/output error". No further information given.
Sorry, my instructions may have been too vague. Yes, when you boot into the Recovery HD on your internal HD and use the Disk Utility Restore you need to specify the Source and Destination as a volume (e.g. Macintosh HD). Don't select the drive. And make sure the SSD is formated correctly.
With Disk Utility's Restore it does a block level copy so it's like creating an "image" in the PC world (e.g. Norton Ghost or Acronis True Image). This means you get ALL visible and hidden partitions copied over and bootable. With CCC you get a bootable clone of your OS/Apps/Data, but you can't boot to a Recovery HD on that clone. There is none. So, when you clone back to an internal drive, CCC has the Disk Center feature to create a Recovery HD on your internal drive. Disk Utility's Restore, however, clones both OS/Apps/Data and the Recovery HD to your internal drive without having to execute a 2nd step.
Which Intel 520 Series SSD did you install? I have an Intel 520 Series 120GB SSD installed in my Mac Mini in the bottom slot (closest to the bottom opening) and my stock 500GB HDD in the upper slot (in the drive bracket).