I have a mid-2010 MacBook Pro, which I want to upgrade with an SSD in the Optical Drive slot and create a Fusion Drive (using the Terminal diskutil command in Recovery Mode) and then re-install OS X Yosemite on the newly created Fusion Drive. I have already upgraded the HDD from 250 GB to 1 TB and the RAM is 8 GB, upgraded from 4 GB.

I need some advice because, while I know quite a lot about software (I study Computer Science at University), I'm not so good on the hardware side of things. So the questions I need answers for are:

  • What would be the best SSD to get for my Mac? I have been looking at the Samsung 840 Evo, but I was wondering whether something like the Samsung 850 Evo would be worth buying instead. Would I get the extra speeds it offers, seeming as my MacBook Pro can only support up to 3 GB/s instead of the 6 GB/s of newer models. Also the SATA connectors are only version 2, not 3.
  • When upgrading it, where do I put the SSD? Before the Fusion Drive came about, I've read that you should put the SSD in the slot where the HDD is, and put the HDD in the Optical Disk slot, as this will avoid problems with Sleep mode (because the SSD will be the boot volume). Is this still necessary with a Fusion Drive, because the system treats the 2 drives as one Logical Volume anyway?
  • Would I need to enable TRIM support with a Fusion Drive? Would the Samsung 840 Evo or anything else like that support all that I need?

Thanks for any help :)

2 Answers 2


re 1: hard to say - if you can spare the Money you should go for the 850 bc. of a (probably) better Garbage Collection (see #3), else go for the 840.

re 2: The best tutorial for replacing the optical drive with a harddrive (or SSD) can be found at iFixit.com, f.e. this one. You should search for the Tutorial for your model, the link i posted is probably not for your model.

re 3: There is a hot discussion going on if Trim should be enabled or not and if that is a bad thing. Fact is, Apple has Trim Support enabled only on its own OEM SSDs and disabled it for third party drive. There are Tools to enable TRIM Support, but it could be a not necessary bc. of a better Garbage Collection within the SSD Firmware (see this article and this Article). For general Infos i recommend this Article from Samsung

BTW, to create a homemade Fusion Drive you need to use the 'Core Storage Volume' Command. You can look it up with

man diskutil

look at the 'coreStorage' section. There are some tutorials for creating a homemade Fusion Drive, but it's a very painful process.

  • Thanks for the advice, seems like enabling TRIM is a bad idea due to the changes in Yosemite. One more question: if I bought a SATA3 drive like the 850 Evo, which offers very high speeds etc, would my older SATA2 connections still be able to access those high speeds or would they be lower? Thanks for the help :)
    – Tom Oakley
    Jan 2, 2015 at 0:37

I have installed quite a share of SSDs in older Macs to give them second breath so to say and can answer your questions from my perspective.

  • What would be the best SSD to get for my Mac?

Just buy cheapest big manufacturer brand. I have been installing Intel 320 (40GB), Micron M4(64GB), Kingston V300(60&120GB), Toshiba OEM(Marvel chip I believe, 128GB), Samsung 830, 840 EVO(120GB), SanDisk Ultra(if I recall right, 128GB). They all are about the same, all can support TRIM, all have about fine GC, speed varies a bit but you will never feel the difference. But price can be quite different and so of course warranty term.

If talking about Samsung EVO specifically then I would now only install it on Windows machine since their selling point is RAPID mode which is only working in Windows. And weakness is TLC cells used for NAND chips.

SATA3vsSATA2 is only applies when doing much of linear writing&reading. I say just don't bother about that.

  • When upgrading it, where do I put the SSD?

In Optibay. You have equal ports in you Macbook and HDD port has Sudden Motion Sensor and rubbered sockets for HDD — why waste it on SSD? Didn't have any problems with sleep in SATA Optibays. I even tried putting SSD into PATA optibays and it was fine too BTW.

  • Would I need to enable TRIM support with a Fusion Drive?

Frankly I don't know. Well for sure you don't need to. But you can if you want that. You can do it with Chameleon SSD Optimiser for example.

Though there is a caveat in Yosemite. Since enabling TRIM on non-Apple drive will patch AppleAHCIBlockStorage.kext signed by Apple you need to disable kext signing and you might not be able to boot into OS X if signing rule be reapplied (like NVRAM will be cleared or so)

And also I never tried to create Fusion drive so I can't comment on that.

  • Thanks for the advice! Seems like enabling TRIM is a bad idea, thanks for highlighting that. I'm still tempted by the Samsung models (probably the 850 Evo) because due to my University course, at some point I will be installing Windows, and will be able to use their RAPID mode. Also based on my research they offer better Garbage Collection and so won't slow down so much (due to TRIM not being enabled). Correct me if I'm wrong. Thanks for the help :)
    – Tom Oakley
    Jan 2, 2015 at 0:39
  • Actually you will get better performance of more free HDD than anything. But I don't know how this can be handled in Fusion drive scenario. And regarding SATA2 — you drive sequential read and write be capped at about 300MBps. You random read&write will largely be unaffected by this. Like here is an article on this kb.sandisk.com/app/answers/detail/a_id/8150/~/…
    – iskra
    Jan 2, 2015 at 0:50

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