Easy 2011 iMac Memory and Hard Drive Upgrade

My iMac (2011, 21.5-inch model) was feeling down.  It was running out of disk space and everything was slowing down to a crawl.

So a about six months ago I decided to upgrade my iMac with a larger hard drive and increased memory, restoring performance to be faster than ever.  It was far cheaper to upgrade my Mac, and it was much easier than I expected.

It took me about 30 minutes to do the upgrades, and my iMac is much, much faster.

Here are the specific parts I used for my upgrade:

Hard Drive

I went with this 4 TB Seagate Hybrid drive for a few reasons:
  1. It's HUGE.  At 4 TB, it is eight times bigger than the stock 500 GB hard drive.
  2. It is affordable.  Per GB, it is far cheaper than any SSD.
  3. Being a "Hybrid" SSD/Hard drive device, it is FAST.  The modern OS really expects fast disk devices. This sped up my Mac a lot.
  4. It is a one-for-one replacement for the old device.  It easily fits inside the case.

[Update: this driver has remained fast and reliable for over a year now]

 Thermal Sensor

To upgrade the hard drive in a 2011 iMac, you need to add either a special temperature sensor or special software to make sure the fans run properly.  I went with the OWC thermal sensor hardware because it is priced somewhat similarly to a software solution, and it should be more reliable than software, which can go out of date.


Memory is cheap, and the 2011 iMac has four (!) slots.  I added this inexpensive 4 GB of memory, and in doing so it brought my available RAM up to 8 GB - which is plenty for the average Mac user.  If you want to go nuts, bigger RAM chips are a possibility - according to Internet lore, you can add four 8GB SIMs to bring it to an unreasonable 32 GB.

Upgrade Instructions

For tools, all I needed was the following items
I used a few different instruction on-line to do this upgrade.  I won't repeat them blow-by-blow, but will just say that I had an easy and trouble-free time using the following directions:

iFixIt Hard Drive upgrade instructions
Excellent printable instructions for upgrading the hard drive, but doesn't cover the thermal sensor.

OWC Hard Drive upgrade video instructions
Video instructions.  Covers the 27" iMac, but it is very very similar to the 21.5"

iFixIt Memory upgrade instructions
Excellent printable instructions for upgrading the memory.

And there you have it!  I personally think that a Mac from 2009 on forward can be inexpensively upgraded to be a fast and speedy machine.  Do it!

UPDATE: Authors Comments
  • I've been running this setup for more than a year now, and I've been very happy.  The machine is much faster than it was, and it has been perfectly reliable.
  • Tools.  When dealing with any mechanical component, you should always use the right tool for the job.  I often hear complains that Macs require "special" tools.  But to be honest, the tools are not special or weird.   The reality is that the proper tools required when working on a Mac are common and inexpensive.

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