What options are available for the "extra" eSATA connector on the 27-Inch "Mid-2010" and 21.5-Inch and 27-Inch "Mid-2011" Aluminum iMac models? How many drive bays do these models have?

The 27-Inch "Mid-2010" Aluminum iMac models -- the iMac "Core i3" 3.2 27-Inch and "Core i5" 2.8 27-Inch -- have three 3 Gb/s Serial ATA connectors -- one for the hard drive, one for the optical drive and an "extra" one for an optional 2.5" SSD in addition to the internal hard drive and optical drive.

The 21.5-Inch and 27-Inch "Mid-2011" models -- the iMac "Core i5" 2.5 21.5-Inch, "Core i5" 2.7 21.5-Inch, iMac "Core i5" 2.7 27-Inch and "Core i5" 3.1 27-Inch -- also have three Serial ATA connectors. However, as first discovered by site sponsor OWC, after updating the system with EFI Update 1.6 (or later), these models are capable of supporting the faster 6 Gb/s Serial ATA 3.0 standard.

Officially, the only option for this third eSATA connector intended for an SSD is the optional Apple installed SSD at the factory. However, other options are available for skilled hardware hackers and those interested in third-party services.

Unofficial Upgrade Options

As also first discovered by OWC -- and directly referencing the "Mid-2010" 27-Inch models -- if an SSD is not installed at the time the system is purchased, the connector cables and mounting bracket are not present for the third Serial ATA connector. It still is possible to install a 2.5" SSD in addition to the hard drive if an SSD is not installed initially it's just a bit of a "hack" as one will have to find a way to mount it place. Consequently, its debatable whether or not this is really a "drive bay" in the traditional sense, but it is a space in the system capable of holding an SSD and its not unreasonable to think of it as a third drive bay.

However, as well as providing the option to install an SSD "up to 40% faster than the factory offered SSD" in the third "drive bay," or replacing the hard drive and/or optical drive with an SSD, OWC also offers to use this third Serial ATA connector to add an external eSATA port on the 27-Inch "Mid-2010" and "Mid-2011" models. OWC likewise offers to install as many as three SSDs in the 21.5-Inch "Mid-2011" models (but an external eSATA port is not an option).

Having OWC perform these upgrades requires one to mail the iMac to the company for professional installation. This video provides more details on the service:

Site sponsor Other World Computing sells hard drives, SSDs, and other upgrades for Aluminum iMac models (and all other Macs) as well as providing the upgrade service by mail for the 27-Inch "Mid-2010" and 21.5-Inch and 27-Inch "Mid-2011" Aluminum iMac models. Mission Repair offers a hard drive upgrade service by mail for all iMacs.

Also see:

• How do you upgrade the hard drive in the "Original," "Early 2008" and "Early 2009" (20-Inch and 24-Inch) Aluminum iMac models? What type of hard drive do they support? Can you swap the hard drive for an SSD?
• How do you upgrade the hard drive in the "Late 2009," "Mid-2010," "Mid-2011" and "Late 2011" (21.5-Inch and 27-Inch) Aluminum iMac models? What type of storage do they support? Is it even possible to upgrade these models?