I had already put in a 500GB 7200rpm Seagate in this way back when I was running out of space. So the next thing to do is to upgrade the hard drive. Furthermore, because of the decline use of the Superdrive, i.e. haven’t used it in 3 years, I decided to swap it out and put a hard drive chassis in there as well so that I can have a bit more space.
This is where the interesting thing happened, I had read online about how to make a Fusion Drive if you managed to have an internal solid state drive (SSD) and an internal hard drive (HD). The concept of the Fusion Drive is simple, pair an SSD together with an HD and use it so that the frequently accessed data is usually on the SSD. So the ‘usual’ speed of data access is that of the SSD, but it allows for a larger storage at a slower speed if you ever need to access that information again in the future.
The Fusion Drive Concept
While it’s similar to the SSD caching, where you have a fast device pair up with a slow device to speed up input and output, but fundamental difference comes in the process in which the devices work together. In the traditional SSD+HD model that’s been around for a while now, data is stored onto the HD and then gets promoted to the SSD as it gets used more often. The base storage unit is the HD. Also, the SSD itself is not that big, somewhere in range of 4-16GB. In the Fusion Drive model, data is stored in the SSD first, and then any surplus is sent to the HD. The system then figures out the data that get used often and promotes/swaps the data between these drives, causing the data that is accessed more often to reside in the SSD. So the SSD is the base storage unit. To support the change in this model, the SSD is now typically 128GB or higher. I think that one of the key things that has made this concept possible is the advances in SSD technology, causing them to be more reliable as main drives and really fast. The other is the concept of the Core Storage from Apple. It was originally used as a way to encrypt your volume. But they managed to bake all this process for the interaction between an SSD and an HD into a mixed hardware Core Storage Volume.
So after a lot of reading, I decided to put one together. To be hones, technically, its not that difficult to do this upgrade, buy some parts and follow the instructions, not much to it. What I found to be the hardest was to select the correct SSD for the job. It had to balance performance, reliability, and price. It was a tough decision, but in the end I went with an Crucial m4. Among my other choices was a Samsung 840 Pro, OCZ Vector, and a OCZ Vertex 4. I think any one of those would have worked pretty well, but because of cost, availability, and my stash of gift cards. the Crucial won out.
I did deviate a little from the set up that’s in the Apple approved Fusion Drives. They run it with a Samsung PM830 128GB SSD, I doubled it to 256GB because I had need more space, and because if this doesn’t work, at least I’ll have a 256GB and I can play with symlinks and other stuff to do a dual HD, non-combined set-up on the MacBook Pro.
One thing of note, be careful when removing the little screws on the edge of the MacBook Pro to take out the Super Drive. I was so close to losing it because I was stripping the screw trying to get it out. Thankfully, the OWC kit came with the necessary screws (due to the higher profile of the Data Doubler frame) so I didn’t have to reuse those ones.
This DIY Fusion Drive was done on a Late 2008 MacBook Pro Unibody (5,1), with a Crucial m4 256GB SSD, a Seagate 500GB 7200rpm Hard Drive, and Mountain Lion.
Once I had all of the hardware set up, I just booted up on a USB drive and loaded up the Terminal, made the Core Data and Core Storage Volume, and installed Mountain Lion on top of it. Everything seems to be working as expected, and I do see movement of data in iostat.
Boot up is a lot faster and frequent tasks seem to also run faster as well. I have filled up the SSD now with photos and apps, so we’ll see how it works over time as I put more and more stuff on the Fusion Drive. I seem to have breathed a little bit more life into my old MacBook Pro, so I think I’ll be able to push up a full system update until the next iteration.
Here are the links for the instructions, concepts, and the parts:
@jollyjinx‘s research and posts in regards to setting up a Fusion Drive
Anandtech’s commentary on A Month with Apple’s Fusion Drive
OWC Data Doubler
Check the gallery for pictures of my dismantled MacBook Pro through this process!