NOTE: The SSD shown in this guide is the older Crucial model (C300), which only acheives half the speed of the newer Crucial m4s. I purchased mine from Adorama for much less, also consider Amazon. Apple will charge you $1699 for this model + tax. I purchased the iMac 27' base model (MC813LL/A), which comes with a 2.7Ghz processor, 4GB of memory, and a 1TB hard drive. Performing the actions herin may void Apple's warranty. This procedure is intended for educational purposes. Although it may be different for a 21.5' iMac, I know it is possible, as I read that many people have had success across the web. This procedure was performed on a 27' iMac which has slightly more room to install an SSD.

Once the SATA cable is installed, it is easy to install and securely mount an SSD drive under the DVD drive. The iMac has two SATA-III connectors, one is already in use by the orginal 1TB hard drive. The procedure requires some dis assembly to connect a SATA cable to the spare SATA-III connector located underneath the motherboard. This is not a replacement for the original hard drive, but instead an addition. This procedure explains how to install an SSD. The total time to complete is 3 hours approximately. Some prior computer experience is recommended along with patience. And after installation, you'll feel more comfortable with your iMac hardware.

To install an SSD on a 2011 Apple iMac is not easy, but not hard either.

Ssd hard drives for imac 27 late 2013