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Mac Pro Storage Upgrade

An SD-PEX40079 with three 256GB Crucial m550 mSATA drives attached.

I’ve been slowly changing my storage habits lately, because I’ve been seduced by the speed of Solid State Drives. When I bought my Mac Pro, I got it with the extortionately expensive Apple SSD. It’s as solid as a rock, and the only thing out there with official TRIM support, but it’s not the speediest option and that’s largely down to the measly 3Gb/s SATA II bus that Apple forgot to upgrade with the 2012 edition. Seriously, guys, you couldn’t have swapped out that controller?

However, because these Mac Pro machines are proper tower systems with PCI-E 2.0, there are options out there. For a long time I was going to go with the Sonnet Tempo SSD Pro (or the Pro Plus as it’s now become) but blimey, at over £200 it’s an expensive way of putting SATA III in your machine. And eSATA is a lovely feature, but not already owning any eSATA caddies, I just didn’t think I’d use it that much.

A little Googling turned up this thread on the TonyMac forum, where ‘gsloan’ had found success with the Syba SD-PEX40068. But would you believe it; discontinued. Nuts.

Finding An Alternative

It seemed reasonable to assume that Syba might have put together a replacement for the SD-PEX40068, but sadly they don’t appear to have another that fitted the bill. I was willing to give anything a shot, but knowing I had to get these things shipped from the US to the UK rather dampened my enthusiasm. There is the SD-PEX40044, but that appears to be a single lane card, which would limit its abilities. I also didn’t really want to start stringing cables around the inside of the case, so that wiped out virtually every other card they do; except for the SD-PEX40079.

SD-PEX40079 - Image courtesy SYBA Multimedia Inc. SD-PEX40079 - Image courtesy SYBA Multimedia Inc. SD-PEX40079 - Image courtesy SYBA Multimedia Inc. SD-PEX40079 - Image courtesy SYBA Multimedia Inc.

The SD-PEX40079 is a 6Gb/s SATA III card, providing four ports or four on-board mSATA mounting points. They list it as a PCI-E 2.0 ×4 card, but it’s driven by the same Marvell 88SE9230 chip as the SD-PEX40068 which only handles PCI-E 2.0 ×2, so I’m not sure where they’re getting that from. However, not bad at all for £60 shipped to the UK.

The real bonus of the SD-PEX40079 is the on-board mounting for mSATA cards. Other than the Apple one I didn’t own any SSDs, so would have to buy them new anyway. Okay, so mSATA isn’t the most popular form factor, but some of the most highly regarded SSDs, such as the Samsung Evo 840 and the Crucial m500 / m550 do come in mSATA format. I struck it lucky at this point and found that Crucial were selling the 256GB m550 mSATA at a discount from their UK store, so I jumped on it and bought three. The SD-PEX40079 was ordered from OutletPC on eBay, and yes, they know that the picture is the wrong one.

The Moment of Struth

Once all the bits were in hand, I hooked up one of the mSATA boards to the SD-PEX40079 and popped it into the Mac Pro. On booting into OS X, I could see plenty of new ‘Generic AHCI Controller’ entries in System Information with 6Gb/s link speeds, which was great, but no sign of the mSATA board. According to the instructions (and they took a little deciphering) the jumpers are all preset to ‘external’ by default. I had to power off and switch all of them to their ’2-3’ positions – then, with OS X booted up and no additional drivers installed, I could suddenly see my new SSDs. Yay!

It’s a bit weird to begin with, but the drives appear as external devices, with the orangey-yellow drive icon in Yosemite. However, in System Information they are listed as ‘Removable: No’. The SSDs are also recognised properly as solid state and not rotational storage, though by default you’ll see that TRIM is not supported. That’s Apple trying to limit you to their own-brand SSDs. If you fire up TRIM Enabler that issue will soon disappear.


I’ll be honest, I didn’t spend massive amounts of time benchmarking these SSDs. At this stage I was rather locked-in to the purchase; so long they were quicker than what I had, that would be fine! I simply employed everyone’s favourite: Blackmagic Disk Speed Test.

Apple SSD on internal SATA II interface. Crucial m550 mSATA SSD in Position 0 of SD-PEX40079. Crucial m550 mSATA SSD in Position 1 of SD-PEX40079. Apple Software RAID 0 of both m550 SSDs.

As you can see, there’s certainly a difference! The Apple drive tops out at 255MB/s read and 240MB/s write. This is perfectly normal; there are two systems I use at work with the same setup, which give exactly the same results.

With the Crucial 256GB m550, I got rather less than the advertised 550MB/s read and 500MB/s write. They both turned in around 485MB/s read and 440MB/s write. I don’t know where those final few MB/s have gone, but there not there for me. However, I always intended to run two of these in RAID 0 for my OS X system. That yields a much more impressive 680MB/s read and 700MB/s write.

Considering the price difference as compared to the more mainstream options, plus the convenience of potentially having four drives on a single card – plus standard SATA ports just in case – I’m really not complaining.

Hardware RAID

The eagle-eyed amongst you may have spotted that the Marvell 88SE9230 controller also supports hardware RAID. You may also have noticed that I’ve not had to install a single driver up to this point. If you want to use hardware RAID you certainly can, but you need to install the management console and configure it all in Windows, as you can’t get to the BIOS control screen with the card installed in a Mac Pro. I did try it out, but to be honest, there are a few problems.

While it certainly works, it’s a bit slower than software RAID; between about 80MB/s slower for RAID 0 in my experience. Also, if you’re in OS X and using RAID 1, how do you tell when a drive has failed and the array is degraded? Well, you can’t. Finally, your SSDs will appear as a rotational storage device in OS X; now I don’t know what difference this really makes, but there’s bound to be something. For these reasons, it’s not a feature I’ll be taking advantage of.

Boot Camp

Once messing around with benchmarks was done with, I decided to set up Boot Camp. The plan was always RAID 0 with two drives for OS X and one separate drive for Windows 7. However, instead of the usual rigmarole with Boot Camp Assistant, I thought I’d go it alone. I reformatted one of the SSDs to a single FAT partition with a GUID Partition Table. Popped in the old Windows 7 disc, rebooted the Mac with the Option / Alt key depressed and chose the Windows CD.

Everything went well, including a brief view of the SD-PEX40079’s BIOS screen showing the connected devices, up until the point of choosing the drive. You could choose it (ignore the 200MB EFI partition) and reformat it to NTFS, but moving on from that hits you with a classic error:

Windows is unable to install to the selected location (0×8030024)


The easiest, quickest way around this is pretty stupid, but it’s the one I went with. Disconnect all the other drives, so that the one Windows is going to install onto is the only one visible to the system. It clears the issue right up, but involved removing the other two mSATA drives and the Apple SSD before the Windows installer would work. Once the installation has completed, everything can go back in as normal; if the wheels come off in the future, I’ve taken a clone of the drive in its current state, so I can just overwrite it from OS X.

After installation the card supported Boot Camp with no troubles at all. All of the normal controls work fine; there’s really no operational difference between a drive on the SATA II bus and one on the card.


So the final part of the jigsaw was putting OS X on the drives with RAID 0. Running from the original SSD, I simply created the array in Disk Utility, then used SuperDuper! to clone the running system. Choose the array in System Preferences, reboot, and everything is fine. Some apps (such as Dropbox) need to be re-authenticated, but other than that it was remarkably straightforward.

It’s good to note that the drive, although still displayed as an external device, is no longer ejectable once you’re booted from it, so you’ve got no worries if you thought you might be able to accidentally unmount your boot drive. Also, finicky features such as sleep work just fine – there’s no catastrophic unmounting when it kicks in.

All in all this was a rather longwinded way of saying that the Syba SD-PEX40079 works very happily in the Mac Pro and is a cheaper alternative to some of the other options. If you’re in the market for an SSD setup in your Mac Pro, it’s well worth bearing in mind.

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