Hi I was thinking about adding an SSD drive inside my iMac mid 2011. I found that you can have both two drives in the iMac as long as you remove the dvd drive.

I want to color correct a short film. The footage is Apple ProRes HQ (data rate around 300mb/s) and the total size 45GB (i found this using tha aja datacalc application).

Would this be a good idea? Or should I buy an external SSD thunderbolt instead? Which set up would be faster?

Also if I buy an external SSD, would a size of 256GB be suitable for the job?

Thank you all in advance, Rafael.

2 Answers 2


The DVD drive is connected via SATA rev. 2.0 / 3Gbit/s. That means the SSD is gonna run at a max. of 300 MB/s approximately.

This link seems to indicate that there's at least a second drive bay (excluding the optical bay) inside the iMac, which runs at SATA rev. 3.0 / 6Gbit/s speed. It would be wiser to use either the second bay or upgrade your primary system SSD.

Since the above link mentions the need to upgrade the EFI firmware, one should be aware the latest firmware updates can be found at the Apple web site "About EFI and SMC firmware updates for Intel-based Mac computers".

If you want to add an internal SSD, you can take a look at the ifixit guides, they can be used as a very good indicator as to how difficult the procedure would be.

I would not recommend an external SSD. They are extremely expensive and don't really give you a plus. Thunderbolt SSDs are even more expensive because of their rarity. If I were you I'd consider the internal upgrade first.

  • Do you know if it is possible to replace the optical drive with the the HDD shipped with the Mac? This HDD drive has a SATA rev. 2.0 interface. If so, then would it be possible to put a SDD with SATA rev 3.0 interface in the bay where the HDD originated? Commented Aug 9, 2016 at 13:49
  • I doubt that the 3.5" HDD fits into the optical bay, so thats not really an option. And even if it did you would have to use an adapter cause the 3.5" SATA+power cables are different from the 2.5" ones. The easiest way to just add an SSD would be following this instruction. However, you need a power adapter which you can get with this kit.
    – sblasher
    Commented Aug 9, 2016 at 14:17
  • Thanks to klanomath for adding the link to the dual HDD kit. Just to add to what I just said: Neither the kit description nor the official iMac site ever mentions if the spare connector is a 3Gb/s or 6Gb/s, but it seems like it is a 6Gb/s one, but don't cite me on that. For the SSD I would suggest an 850 EVO 256GB/ 512GB. They come with 5 years of warranty and they are pretty fast, maxing out the SATA port.
    – sblasher
    Commented Aug 9, 2016 at 14:28
  • This web site shows the availability of an internal SDD SATA 6Gb/s cable for 21.5" iMac 2011 models. Similarly, this web site shows the availability of an internal SDD SATA 6Gb/s cable for 27" iMac 2011 models. Commented Aug 9, 2016 at 16:16
  • The mere fact that the cable is a SATA 3 one doesn't mean that the signal, transfered over it is too. You can use a SATA 3 cable for SATA 2 no problem.
    – sblasher
    Commented Aug 9, 2016 at 16:31

There are basically 4 options available to you. I will go through each one. I happen to have access to a 21.5 inch 2011 iMac. So, I am able to look up some of the specifications by viewing the System Report.

  • Replace the optical drive with a SSD. The current optical drive has a transfer rate of only 1.5 Gb/s while the logic board is capable of 3 Gb/s. Therefore, this option would lead to a transfer rate of no more that 3 Gb/s. This is usually far slower than the internal transfer rate of a typical SSD. Therefore, this is probably your worst option.
  • Replace you HDD with a SSD. With the proper firmware upgrade, the logical board will be able to transfer data to a SSD at a theoretical rate of 6GB/s. The problem here is the your Mac was not designed for this situation. The power cable connection to your HDD has additional signals that determine the temperature of your HDD. Replacing with SSD will require inserting a aftermarket conversion cable between the existing power cable and the SSD. This cable will also have a temperature sensor you will need to attach to the outside of the SSD. This option may not be desirable, because you will loose your existing internal HDD. You will also need to purchase a kit, with conversion cable and 3.5" drive converter bracket, to install this drive.
  • Add a SSD without replacing the HDD. This option will be far harder to install than the previous two options. Again, with the proper firmware upgrade, the logical board will be able to transfer data to a SSD at a theoretical rate of 6GB/s. You will also need to purchase a mounting kit with cables to install this drive.
  • Purchase an external Thunderbolt drive. The Thunderbolt interface operates a 10Gb/s which exceeds the internal transfer speeds of a SSD. So this option would not be slower that any of the previous options. Most of these types of drives also come with a USB 3 interface. This may come in useful, if you need to use the drive with the latest PC models.

As for the size of the SSD. Sorry, I can not help you there.

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