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Adding SSD and new big HD as Fusion Drive to iMac

richardblue -

iMac Intel 21.5" EMC 2428

Installing iMac Intel 21.5" EMC 2428 Dual Drive Kit

Installing iMac Intel 21.5" EMC 2428 Dual Drive Kit

1 - 4 uren


Mijn probleem

IMac 21.5" Mid 2011 running slow due to fullish 500GB original HD. Wanted SSD for speed, big HDD for storage. Apple "Fusion Drive" capability automatically manage this.

Mijn oplossing

iFixit kit and instructions are great. Very clear. Just work slowly. Tape down the wires as you unplug them - especially from the main logic board. Remove the RAM before starting.

Whilst the machine was open, I also upgraded the HD to a larger drive, using these instructions, starting at Step 10, after completing all the steps of the Dual Hard Drive installation guide.

iMac Intel 21.5" EMC 2428 Hard Drive Replacement

Mijn advies


One main issue - the Mac fans ran very fast after upgrade. Both the CPU fan and HD fan (not the Optical Disk Drive one). Maybe I did something wrong but there are lots of reports online of this being an issue with Yosemite with replacement hard disks and SSDs on iMacs.

If you Google you'll see several Mac "fan control" programs. I tried 4 of them til I found one that actually worked for me --- "Macs Fan Control" by CrystalIdea software.

Free and worked for me

iStats Menus is also useful to monitor all the temperatures in the Mac (but its fan control feature did nothing for me):


This is useful for doing a "clean install" of Yosemite onto your new drive, especially if you use a fast USB3 Flash Drive:


Additionally before you do the OS install, for "extra points", if you have an SSD and an HDD with a recent Mac OS you can make them into your own "Fusion Drive". Apple came up with this a couple of years ago -- "the speed of an SSD and the space of an HDD". They charge ~$500 extra for Fusion Drives on new Macs. Turns out this appears to just be software that's already built into recent OSX version. Very slick. It "fuses" the SSD and HDD together and OSX manages which files should go where and automatically moves files you use often to the SSD for speed and moves ones you use less to the HDD for capacity. I now have a single "Fusion Drive" with 2TB+128GB capacity.

This is very easy to do using instructions below. First backup everything (a completely separate Time Machine backup is good). I then installed the new 128 GB SSD and 2 TB HDD into the iMac using the iFixit instructions and kit. Take the old drive and attach it using a USB drive adapter, e.g.

Universal Drive Adapter

Follow the instructions to create the Fusion Drive here:

There are other sets of Fusion Drive instructions out there without the Recovery Partition. What I did was to first do an OSX install onto the SSD which creates the recovery partition for you. THEN create the Fusion Drive, using only the "data" partition on the SSD, leaving the Recovery Partition in place.

Once the Fusion Drive is created:

1) Install OSX onto the Fusion Drive (the prior install and the other contents of the SSD, other than the Recovery Partition, get wiped when you create the Fusion Drive)

2) Use Migration Assistant (in Applications/Utilities) and your old drive connected via the external USB adapter to move all your apps, docs, etc back in to place on your new Fusion Drive.

Some of these steps take a while to run (several hours for me) but you can walk away and let them run unattended, e.g. overnight. I'd allow a weekend to do this if this is your work machine.

Very happy with the results

Anti-Static Project Tray Afbeelding
Anti-Static Project Tray


iMac Intel 21.5" (Mid 2011) Dual Hard Drive Kit Afbeelding
iMac Intel 21.5" (Mid 2011) Dual Hard Drive Kit


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Is it possible that after the creation of the fusion drive, I do not go through the steps of reinstalling os x, but instead clone the entire content of my old non-fusion drive onto the fusion drive? would this work?

ellcara - Antwoord

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