iMac 27" Late 2009 can I replace optical with SSD as main boot drive

On the 11,1, both ports are SATA2. So replacing the ODD makes more sense, as the HDD has custom firmware so the EFI can monitor the temp. Replacing the ODD is fairly simple with a #10 Torx driver.

Pick up an sad caddy for a Macbook Pro on Amazon. (about $11). You may need to modify it a bit to fit into the ODD frame in the iMac, the screws may not line up nicely.

Use ifixit to get the unit open, you can do it without suction cups. Just make sure you get the thermostat cables all reconnected. (I learned that one the hard way)

The ODD bay has a sensor taped to the drive, it's very easy to pop it off and attach it to the SSD.

Just created a fusion drive and everything runs fine and fast . I used a samsung 830 256GB ( disk0) in the optical bay, and the internal 2G ( disk1) in my iMac late 2009 i7 and used this guide :

http://www.petralli.net/2012/10/anal...nal-hard-disk/

Did a fresh install of 10.8.2 on the new drive and used migration assistant to migrate from my Supersuper clone of the "old" disk (800 GB )
Worked like a charm

No need to buy a fancy caddy etc. Just get an adapter to connect the SSD and use the case from the optical drive. I used plastic strips and the SSD sits rock solid. (see picture)

this is the adapter you need :
http://www.av-cables.dk/sata-stroem-adapter/stroemadapter-22pin-sata-til-13pin-slimline-sata.html

Enjoy

haha .. you may want to cover or block the disk slot ... if someone sticks a disk in there, you will have to disassemble the iMac to get it out.

late 09 you can swap out both the HDD & Optical drive without problem with newer drives, no special firmware or issues should arise