Successful DIY Fusion Drive on Early 2008 iMac

Discussion in 'OS X Mountain Lion (10.8)' started by amethystjw, Mar 9, 2013.

  1. amethystjw, Mar 9, 2013
    Last edited: Mar 9, 2013

    amethystjw macrumors member


    Aug 28, 2008
    Livonia, MI
    I set out to create a Fusion Drive in my early 2008 20" aluminum iMac and was (apparently!) successful. I’ve only been using it for one day, but so far it is working very well. I’ve included a simple graph showing performance comparisons in seconds. In case anyone with a similar iMac wants to try this, I thought I'd describe what I did.


    I bought my early 2008 iMac new and have had very few problems with it. This is a fantastic model, in my opinion. Over the years I have upgraded the RAM from 2GB to 4GB (that’s the maximum) and the 320GB hard disk drive to 1TB. For being a 5-year-old computer, it runs extremely well, although it feels a little slow at times and the optical drive is starting to fail.

    Late last year Apple released new iMacs and Mac minis with an optional feature called Fusion Drive, which essentially fuses together a 128GB solid state drive (SSD) and a standard large hard disk drive (HDD) in such a way that the operating system sees just one disk drive. The cool thing is that the OS keeps track of what data you access most often and moves that data to the SSD automatically, dramatically speeding up disk access times on the computer.

    When I heard about this I wanted to try it myself and I found some very helpful resources online describing how to do it. Most required an external disk drive, but I didn’t want to rely on an external disk in order for my iMac to function, so I tried something else: I removed the faulty optical disk drive and replaced it with a 2.5” laptop HDD. I then replaced my old HDD with a new SSD. When I ran the commands required to combine the two new disks into a single “logical volume” I was able to reinstall OS X 10.8.2 and restore my data from a Time Machine backup. My computer now looks and feels just like it did before, right down to the position of the icons on my desktop, except it has no optical disk drive (I don’t care; I use an external one.) and it is really, really fast.

    Want specifics? This should point you in the right direction:

    Patrick Stein did some excellent testing to verify that Fusion Drive technology is possible on an older Mac here:

    He is careful in his later posts to warn people that he does not trust Apple’s default file system with his data and thus does not recommend creating a Fusion Drive on an important Mac. That said, I read his post, was convinced that it would work, and did what he recommended. You can find more straightforward directions here: has the best step-by-step repair directions on the web. Their guide showing how to replace my iMac’s optical drive with a hard disk drive is superb:

    This is what I actually did:

    1) Using Winclone 3.7 ($20 and totally worth the price!) I backed up my Boot Camp partition to a file on my hard disk drive. The Boot Camp partition was about 40GB and this took close to an hour. I have Windows XP installed on it. What can I say? I’m old school like that.

    2) I backed up all of my data, including that Boot Camp partition backup file, to my Apple Time Capsule using Time Machine. I had about 724GB of data on my HDD. Using a USB or Firewire backup hard disk drive would also work fine.

    3) I created a bootable Mountain Lion 10.8.2 USB flash drive using an 8GB flash drive I picked up from a local store for $12 US. These directions are very helpful for doing this:

    4) I ordered parts. I ordered a 2.5” fast HDD from NewEgg for $89. I used a Hitachi GST Travelstar 0S03563 1TB 7200 rpm with 32MB cache. I bought a cheap 128GB SSD on eBay for $76. The one I bought is a Samsung MZ7PA128HMCD-010H1. In order to get the SSD to work in place of my broken optical drive I had to buy an adapter. Luckily, I found exactly the one I needed at for $60:"_emc_2133_and_2210

    5) I disassembled my iMac very carefully and blew the dust out of it while I had it apart. I removed the old hard disk drive and set it aside. I plan to keep it around for a few weeks just in case the Fusion Drive setup fails and I need to go back to the old setup quickly. The SSD is the same size as a 2.5” laptop hard drive, but this iMac uses a standard 3.5” desktop hard drive, so I needed an adapter to make the SSD fit. Unfortunately the adapter I had on hand made the SSD sit about a half inch too far from the SATA data and power cables, and they couldn’t reach. I ended up using very strong Velcro to attach the SSD to the inside back wall of the iMac. It does not look pretty but it works well and is not going anywhere. I installed the 1TB HDD in place of my broken optical drive using the iFixIt guide mentioned above. Unfortunately the adapter I bought from them is about 2mm narrower than a real optical drive, so the screw holes do not line up. I had to drill out the black plastic bracket to make the screws reach. Again, not the prettiest job, but it worked just fine. I put it all back together. This took about an hour and a half but can be done in half that time if someone is already familiar with the inside of this iMac.

    6) I booted it up using the Mountain Lion boot flash drive mentioned above. (Hold the Option key while booting to select the boot device you want.) Instead of installing the OS, I opened Terminal from the menu at the top of the screen and entered the commands described in the articles from Macworld and Patrick Stein. When this was complete, I rebooted, started up from the flash drive again, and proceeded to install OS X 10.8.2. At the end of the installation I chose to restore data from a Time Machine backup. Up to this point the whole process took about three hours. Restoring my 724GB of data took all night over a gigabit network cable.

    7) When the restore was done I rebooted and my computer looked just like it did before I started, but was noticeably faster! I still had to restore my Boot Camp partition, which contained a working (and legal) copy of Windows XP.

    8) I started Boot Camp Assistant and checked the box for “Install Windows 7”, even though this is not what I wanted to do. I set the partition size to 80GB (Use whatever size makes sense for your Windows installation.) and let it rip. The disk was partitioned automatically, but only after I inserted a valid Windows 7 DVD in my external optical disk drive. I don’t know how I would have gotten around this step if I had not had a Windows 7 disc and an optical drive lying around. Any suggestions? I’m curious to hear what others have tried.

    9) When the partition was created, I exited Boot Camp Assistant and ejected the Windows 7 DVD. I used Winclone to restore my Boot Camp partition from the backup file I had created back in the first step. When this was done (about an hour later) my Windows XP partition was intact and worked just fine. The only problem I noticed with it is that shutting down causes Windows XP to blue-screen, and I haven’t spent any time trying to fix that. Since this only happens right at shutdown, I don’t care, so I probably won’t try to fix it.

    10) That’s it! I am amazed at how well OS X runs like this. I did see iTunes crash once a few hours after doing this, and I have only been using the computer with my DIY Fusion Drive for about one full day, but otherwise it seems fine. If I end up with some horrible failure after a week or a month I’ll update this post!

    I hope this is useful to someone. This project took about four hours, not counting the time it takes to wait for long steps to complete on their own, and cost me about $257. The result is that my iMac runs significantly faster than it was designed to, and I plan to get at least another year or two of service out of it!
  2. amethystjw thread starter macrumors member


    Aug 28, 2008
    Livonia, MI
    Update on this project

    I wanted to give a little update to anyone who is interested. Two months have passed since I did this project. This iMac has received light to moderate use over that time and has shown no ill effects! I was able to successfully back up the boot partition to a USB 1TB backup hard disk drive with Carbon Copy Cloner and then boot from that (slow!) drive. I half expected this to fail, but it worked flawlessly. The computer runs fast and is quieter than it was initially, which is saying something because this has always been a very quiet computer.

    All in all I'm very pleased with the way this project has turned out! I'm only disappointed at the lack of interest in this post; if you have attempted this or are considering it or just have a question or comment, please leave a reply here. As it is I am not sure that anyone has even read through the post. :) -Joe
  3. chevelleguy3 macrumors regular

    Apr 24, 2013
    Mckinney, TX
    I too have done a DIY Fusion drive and I think it works great. I'm a pretty heavy Mac user too.

    I am running my Fusion setup in a 13" Macbook Pro Mid 2010. The MacBook has maxed out 8GB of RAM and was still a bit slow. I hate to drop a ton of cash on a new machine so I figured I'd give the Fusion setup a try.

    I went with the OWC 120GB 3G SSD and OWC Data Doubler. Yes I did the 3G drive since my Mid 2010 MBP is only 3.0 Gb/s data transfer on the SATA ports. My internal drive is a 500GB Seagate 7200 RPM drive. I moved the Seagate to the Optical drive in the Data Doubler and put the SSD in the main bay.

    The setup is very easy to do. The machine is pretty quick now. Boot time went from well over 1 minute down to about 14 seconds. Overall, it is much faster.

    I would have done the SSD as stand-alone, but I wanted the drives merged as one. My Mac Pro on the other hand, I'm okay with moving data to another drive.
  4. Emiliano macrumors newbie

    Jun 3, 2013
    Did the upgrade too on my mid 2008 iMac 24", the fusion drive works like a charm! Combined a Samsung 840 Pro 128GB on my old hdd slot, with bracket, and a WD Blue 1 TB in the optical drive caddy. Boot times are now around 15 s, and every application is up and running within 4 sec.
    I read elsewhere that the fusion drive got slower as the SSD's capacity was used more and more. So far I'm on 250 of 1126 GB and there was no significant difference before or after my Time Machine Migration.
    Thanks for your description! Made my week after the original WD500Gb crashed after 5 years of service.
  5. Brian33 macrumors 6502a

    Apr 30, 2008
    USA (Virginia)
    I want to heartily thank the three posters, and especially amethystjw! I am considering the same operation on my Early 2008 24" Alu iMac 2.8 GHz Core 2 Duo (

    A couple of questions, if anyone can help me make sure I've got all my bases covered...

    I also have an XP BootCamp partition and a legal full XP install disk. I would like to use WinClone as amethystjw did to back it up and restore it. Would I still need a Windows 7 install disk to create the boot camp partition? I seem to remember seeing somewhere that Mountain Lion does not allow XP for BootCamp, is this right?

    Also, I am wondering about the SATA link speed for the new HDD once it's installed in the optical bay. Will it have a 3 Gbps negotiated link speed or a 1.5 Gbps negotiated link speed? System Profiler for my "Serial-ATA" shows:
    Link Speed: 3 Gigabit
    Negotiated Link Speed: 3 Gigabit
    and then my current boot drive under that, but doesn't give any info about the optical bay. Also, the PATA Optical Bay SATA Hard Drive Enclosure I'm looking at apparently converts the SATA drive to a Parallel ATA interface???

    Basically I'm trying to ensure that the interface to the new HDD I put into the optical bay will be at least as fast as my current boot drive (SATA 3 Gbps) (or, at least fast enough that the new drive can't saturate it.)

    If someone could use System Profiler to check the link speed on their optical bay HDD, I'd be happy to hear about it.

    Thanks again for all the info and luck with Fusion Drive. I'll have to upgrade (I'm still on 10.6.8), but I think Fusion Drive would be great for me.
  6. amethystjw thread starter macrumors member


    Aug 28, 2008
    Livonia, MI
    Brian33, I'm glad you liked the write-up! I don't see a Link Speed on the ATA category of System Profiler. I don't think ATA has different speeds. (ATA is often referred to as PATA, by the way.) That said, my setup is very fast, so I don't really care what the actual link speed is on the traditional hard disk drive.

    Regarding your question about the drive bay adapter converting SATA to PATA, yes, that's correct. This is actually nothing novel. I was using a converter similar to this in an old PC about ten years ago because I had spare PATA drives and my motherboard supported a bunch of SATA devices.

    Oh, and yes, unfortunately you need a bootable Windows 7 disc in order to create a Boot Camp partition in Mountain Lion. I have still not heard of a way around that. For what it's worth it seems to work using a Win7 disc that comes with a PC, so you can borrow the one that came with your mom's crumby Dell Inspiron. :)
  7. Brian33 macrumors 6502a

    Apr 30, 2008
    USA (Virginia)
    amethystjw, thanks for the clarifications about ATA/PATA. For some wacky reason, I thought when I installed my new 2.5" SATA drive in the optical bay it would somehow magically be on a SATA interface. I forgot to investigate what the PATA part of the adapter's name was about...

    Also, I completely missed the ATA section in System Profiler! However, mine shows no information about the Bus, either. It seems like it should, though, because there were a lot of different ATA speeds (e.g., 33, 66.7, 100, and 133 MBps) List of Device Bit Rates (wikipedia). All of these are slower than the earliest SATA I (150 MBps).

    So, that still made me wonder if the throughput of the HDD in the optical bay would be limited by the PATA interface.

    Of course, the bus need be only as fast as the drive can supply data. According to Hard Drive Performance (wikipedia):

    "As of 2010, a typical 7200 RPM desktop HDD has a sustained "disk-to-buffer" data transfer rate up to 1030 Mbit/s.[29] This rate depends on the track location, so it will be higher for data on the outer tracks (where there are more data sectors) and lower toward the inner tracks (where there are fewer data sectors); and is generally somewhat higher for 10,000 RPM drives."

    So 1030 Mbps = ~ 129 MBps (or is it 103 MBps?). It appears that the two fastest ATAs of 100 and 133 MBps would be close enough, especially because real-world use the HDD is much more limited by seek time and rotational latency than by the transfer rate on the bus (ATA standards versions, transfer rates, and features (wikipedia).

    So I expect there would be no performance penalty by putting the HDD on the ATA bus. I'm probably going overboard, but I just would feel more warm fuzzies if I knew the transfer rate on my iMac's ATA bus!

    The problem with getting the BootCamp partition made has me stymied, at least temporarily, but I'm sure glad I know about it. I really don't want to buy Windows 7, as XP is doing all that I need (playing a glider flight simulator).

    Sorry about the long post, but writing this out at least clarifies the issues for me.

    Oh, amethystjw maybe I have a little tidbit for you: it appears that your iMac can actually work with 6 MB of RAM, despite what Apple says. I'm running 6 MB in mine, tested and runs just fine! Check out your iMac on I've got one 2 MB and one 4 MB so-dimm. (Patriot PSD24G8002S). So there's still another upgrade you can do!

  8. kirsch92 macrumors member

    Apr 30, 2009
    Funny, I found this thread looking for my imac 8,1 pata bus speed!

    I am considering doing the same thing, esp if PATA bus speeds are 100 or 133, because I'm just looking for the drive to be at least as fast as FW800.

    Not necessarily looking at doing fusion, but if I can get OS and apps on SSD, and other data on 7200 rpm drive and be faster that ext FW800 as my only other option besides a giant SSD to hold it all, I figure I am ahead of the game.

    I'll keep looking and let you know if I find something.
  9. Brian33 macrumors 6502a

    Apr 30, 2008
    USA (Virginia)
    Bootable non-Apple optical drive?

    I've changed my plans, at least for now. Anybody putting an SSD into an iMac and taking out the optical drive it came with, may be interested to know that they probably won't be able to upgrade the SSD's firmware without taking opening up the iMac again (unless they choose an OWC SSD?).

    I chose a Plextor SSD, in large part because it has a firmware upgrade procedure that should work on a Mac -- you burn their .iso file to make a bootable CD or DVD, and boot your machine into their firmware utility to flash the SSD. (Before I ordered the SSD, I created such a bootable CD and it worked and the utility appeared to run OK, although it obviously didn't find an SSD to upgrade.)

    Crucial has a similar procedure, I believe. All the other SSD makers (except OWC) only support using a Windows environment to do a firmware upgrade. (OWC may have a OS X utility... I haven't investigated it much.)

    I didn't want to rely on having Windows running on my iMac (although I do have a VM in Parallels), so I thought the bootable-CD would be a better method.

    The problem is getting a Mac to boot from an external optical drive. From what I've read, any Mac that originally came with an internal optical drive will not boot from an external optical drive, not even Apple's own external Superdrive. (It only works for MacBook Airs, and newer Mac Minis and iMacs that don't have built-in optical drives.)

    I did come across several hacks, including patching the driver (kext) files, editing a system plist, and using the nvram command to set boot-args:


    Since there's a pretty good chance SSD firmware might need to be upgraded, I want to keep a optical drive boot capability. Does anyone know if the above hacks (especially the nvram bootargs one) work with non-Apple optical drives to make them bootable???
  10. amethystjw thread starter macrumors member


    Aug 28, 2008
    Livonia, MI
    Brian, I'm no expert in this regard and don't have time the check out the hacks you linked to, but one easy workaround could be to restore the ISO file to a flash drive using Disk Utility and boot from that. I know that my early-2008 iMac can boot from a flash drive with no trouble. It'll be much faster than burning a disc and booting from it, too.
  11. Brian33 macrumors 6502a

    Apr 30, 2008
    USA (Virginia)
    Thanks; I've tried that. I've tried seemingly every set of instructions on the web, using both Disk Utility and the "dd" command, and I can't get my iMac to boot this particular .iso file from USB or from an external Firewire drive. It does boot the .iso fine from the internal CD drive. (It's a Plextor SSD firmware upgrade utility.)

    I know my iMac can boot from a USB, at least it can boot Mountain Lion that way, so I don't think that's the problem. I think it has something to do with the particular format this particular .iso is in. I've tried Disk Utility's "convert" and I've tried "hdiutil -convert", but then I get an error message from Disk Utility about "invalid format" or some such.

    I've given up on that approach and decided to buy an Apple USB Superdrive and will try the sudo nvram boot-args=”mbasd=1″ hack to make it bootable for my iMac (

    I'm acquiring all the bits I'll need for my project. I'll probably actually start around the middle of August (due to an upcoming vacation).

    One question I have for you, amethystjw: is your XP BootCamp partition working OK except for the shutdown? Did you ever figure out how to prevent the shutdown blue screen?

  12. uwranger macrumors newbie

    Nov 18, 2013
    Anyway to do this keeping optical drive intact?

    I have an early 2008 iMac and would like to run through this procedure, but occasionally use the optical drive to burn cds and dvds. Is there any way to do this while preserving the optical drive? Maybe putting the HDD in external USB or FW enclosure? Any confirmation or recommendations would be most appreciated!
  13. amethystjw thread starter macrumors member


    Aug 28, 2008
    Livonia, MI
    Yes, but it won't be as fast. You can use a FireWire or (shudder) USB hard disk drive as the large disk and leave the optical drive in place. I haven't done this but I understand lots of others have.
  14. Brian33 macrumors 6502a

    Apr 30, 2008
    USA (Virginia)
    I think if you put the HDD in an external enclosure, you won't be able to use it as part of a Fusion drive, which would be a real shame.

    I recommend the approach I took :) (which was successful, BTW): put the HDD in the optical bay and buy an external USB optical drive. I got an Apple one, but if you're only concerned about burning DVDs (and not booting from it), you should be able to save money and buy pretty much any USB DVD burner.
  15. jaredbcook, Dec 4, 2013
    Last edited: Dec 9, 2013

    jaredbcook macrumors newbie

    May 17, 2011
    SSD performance when connected via PATA vs SATA?

    I'd like to put a SSD in my early 2008 iMac and maybe do this DIY Fusion Drive, but want to get the best performance possible.

    1. Does the PATA interface limit the throughput of the SSD? How much?
    2. Would performance be any different if I replaced the main SATA HD with the SSD and get a 2.5" HD to put in place of the PATA optical drive (versus just putting the SSD in place of the optical drive)?
    3. Is there another available SATA port that I could use and ditch the PATA cable entirely? Would it even be possible to route a second SATA cable to where the optical drive currently sits, or put the SSD and a 2.5" HD together in the 3.5" bay, each with its own SATA connector?

  16. amethystjw thread starter macrumors member


    Aug 28, 2008
    Livonia, MI
    Yosemite works!

    Just a quick public service announcement -- I downloaded and installed Yosemite on this 2008 iMac with the DIY Fusion Drive and it works just fine so far. During the installation at one point it complained about insufficient disk space (not true) and the only option was to restart. I thought it would roll back to Mavericks, but nope -- the installation continued and it's working. I read about the error online and found others with DIY Fusion Drives who experienced the same error (and one guy with a factory one).
  17. Brian33 macrumors 6502a

    Apr 30, 2008
    USA (Virginia)
    Hey, thanks for that update! It's good to know that I can go to Yosemite with my DIY Fusion drive 2008 iMac when I'm ready (which isn't yet).

    One thing that concerns me is the issue about Yosemite and Trim support for non-Apple SSDs. As I understand it, I wouldn't be able to enable Trim for my SSD without disabling Yosemite's feature that checks for kext (kernel extension) signing. I'm not (yet) sure about all of the ramifications of disabling the kext signing check.

    amethystjw, do you have Trim enabled or disabled for your Fusion drive SSD in your new Yosemite installation?

    In the meantime, I'm very happy with my DIY Fusion under Mountain Lion. This old machine works wonderfully and I love the 24" screen size....
  18. andrewbuilder macrumors newbie

    May 6, 2015
    Sydney, Australia
    RAM upgrade

    Thanks for the article.

    Thought I'd let you know that I have a 2008 iMac 8,1 and have 6GB SDRAM running in the machine without any issues... maybe you can increase the RAM in your machine?

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