do you think you could run the os on an external ssd over thunderbolt.
I don't have thunderbolt on my current iMac (late 2010) but i have bought a late 2012 which probably will arrive next week some time, so i was wondering what are the properties of thunderbolt drives etc.
Comparing the speeds may be of interest to you.
Back in the 1980's and 1990's we used parallel ATA (PATA)-connected hard drives. PATA max transfer speed was 133 MB/s.
In 2003, serial ATA (SATA) replaced PATA. SATA I had a maximum speed of 1.5 Gbps (150 MB/s throughput).
SATA II, still found on some older Macs (some 2009 and earlier) had a maximum speed of 3 Gbps (300 MB/s throughput).
SATA III, the standard on all current hard drives and solid state drives (except for the "blade"-style SSDs, which Apple uses), has a maximum speed of 6 Gbps (600 MB/s throughput).
Thunderbolt revision 1 supports speeds of 10 Gbps. Most Macs with Thunderbolt use this.
Thunderbolt revision 2 supports speeds of 20 Gbps. Of the iMac line, only the retina iMac offers Thunderbolt 2 at the moment.
If you're chaining multiple data-heavy devices off of a single port then performance may dip, but otherwise you can see that speed-wise Thunderbolt offers you the same performance as if the drive were connected internally.