Mountain Lion introduces an additional level of abstraction into the disk stuff, referred to as Core Storage.
The RAID routines were all changed. Users have had a very hard time with bootable RAIDs and with drives without a Recovery_HD partition.
If you are doing high speed Video or Audio production, you will get more of an overall speed boost by getting everything else (except System, Library, Applications, and the hidden unix files including paging/swap) OFF the Boot Drive, so that the incessant Mac OS X "snacking" for another page of this or that does not wreck the speed of your production drives.
That makes sense so let me mention my reasoning for RAID, I need the production increase with speed because I use a very large production library for recording in Logic and it takes time to load all of my software instruments and think the RAID will make my time issues significantly better.
So with this said, do I simply install MT Lion as I did when I upgraded? My Idea is to create the RAID, use time machine backup to place into my RAID (including OS 10.8) and beleieve I can be off and running. My backup will be Time machine as well as perhaps other clones.
Am I correct in my thinking?
Get a decent large enough SSD boot drive for system OS and apps.
Separate drives also helps improve performance because they are not queueing and waiting.
Use RAID for large media libraries that won't fit and be accomodated by a single drive.
After all you have options like $200 1TB 10K WD VR t oday, or 4TB Seagate, both are 180MB/sec and high performance.
Or there are your PCIe SATA SSD storage devices ($$$) of 960GB (and there are people using a pair for 1,8TB and highest performance).
"Perhaps?" No, you really never want to put all your eggs in one basket. Redundant, duplicate, sets and methods. Even RAID6 arrays - I've seen where two such were used.
You do not need or want an array for the system boot drive though.
You almost have to install and plan to keep a non-array system drive today and then clone the system onto the array. Arrays can't have a recovery partition.
RAID 0 is not INHERENTLY faster than individual drives.
RAID 0 gets its speed when reading ONE file or Writing ONE file when it can seek for the next "slice" using the B drive after it has already started tranferring from the A drive. It gets a substantial speedup with ONE file, and falls back to the same speed as individual drives as soon as you move the heads anywhere else for any other reason.
If your workflow involves Repeats of: "reading, processing, writing"; you get better results with a Source drive and a Destination drive, because each time you move the heads to write instead of read, the RAID speed advantage disappears!