Other World Computing

The Fastest; Accelsior PCI Express SSD

Long Term Test

OWC stands for Other World Computing, a title which I felt was very apt for this article. Since I started using OWC’s adapter for modifying my Mac Pro to take multiple SSDs in the optical bay and installing their blisteringly fast SSD into the optical bay of my MacBook Pro, I’ve become a fan of this company. Their adapters and SSDs just seem out of this world; great design, well made and extremely fast.

It was with great interest when I first heard that a PCI Express SSD card was going to be introduced by the company. The advantages of using a PCI Express SSD card are numerous. Firstly, one is directly plugging into the motherboard, using the fastest interface, without having to go through the SATA connectors, adding some speed to operation. Secondly, it frees up your SATA connectors and drive bays for more SSDs or conventional hard drives for storage. In my Mac Pro, I now have four conventional hard drives in the drive bays which I use to store my RAW files amongst other data including documents, music, video and so on. I also have two SSDs installed in the optical bays. One is used to clone the Accelsior every night which is my OS drive, and the other is used for video files when editing  a project. Having FCP X run on the OWC Accelsior and the ProRes 422 video files run from a OCZ 120Gb SSD makes for a very fast and fluid editing experience.

If you’re on a PC, the Accelsior will also work. Regardless of which system you’re using, the helpful thing is the card does not need a driver, so will just work once installed. On a Mac, you will naturally need a Mac Pro as the iMac does not have PCI Express slots.

I decided to go for the 240Gb version which is enough space to store the OS, applications and Documents. Via iTunes I did move the iTunes folder to another drive though as it was simply too big. The card uses Sandforce controllers and several systems to ensure that the SSD chips are used efficiently and kept running smoothly. The SSDs themselves are on smaller circuit boards which clip into the PCI Express daughter card; this means that in time if you want to upgrade to a larger size, it’s easily done.


Using OWC’s own figures, comparing their top of the range traditional SSD (Pro 6G) to the Accelsior makes interesting reading.

OWC Mercury Extreme Pro 6G – Read 559MB/s Write 527MB/s (Peak Data Rate)
OWC Mercury Accelsior  – Read 762MB/s Write 763MB/s
Traditional 5400rpm Hard Drive – Read 75MB/s Write 77MB/s

These are test figures so real life use will vary, but it will vary proportionally, so the speed advantages are clear to see.

Compared to my previous OS SSD, the OCZ Vertex 3 Max IOPS which was very quick, the speed advantage of the OWC Acceslior is immediately noticeable, even without timing.

I did perform some comparisons though using my early 2009 model Mac Pro.


Speed isn’t the only consideration to have though. I’ve had the Accelsior installed in my main imaging workstation, a Mac Pro, for three months now. It has performed without a single hiccup. I installed it when running OS Lion, cloned the OS drive onto the Accelsior using the superb CCC and upgraded to OS Mountain Lion a few days after it’s release. My Mac Pro is on 24/7, used for photo editing, photo archive use, Giclée printing, video and audio editing and general computing too. It’s hooked up to a Sonnet D800 raid with a PCI Express RAID card as well as countless other peripherals and I didn’t have a single issue at all! The Accelsior just performed with 100% absolute reliability and speed.

Final Thoughts

As new technologies come and go and we take leaps forwards, some leaps are giant. The leap to SSDs being one. They are still too costly for storage, but for using as our OS and program disks, the capacities are more than there and the prices have dropped to affordable levels. Although purely on paper the jump to PCI SSD doesn’t appear huge, it is much more than just the speed increase; it’s the convenience increase of freeing up a drive bay for storage too. I for one can’t recommend SSDs highly enough; however if you have a machine with compatible PCI Express slots, then the OWC Accelsior is an absolute no brainer. You’ll love it!

European Buyers – Macupgrade has kindly offered readers of this blog a 10% discount with the code: macupgradephoto

10 responses to “Other World Computing

  1. I too have an OWC Excelssior which I got back in June and fitted to my mid-2010 MacPro. To say the performance is outstanding is an understatement! As a software developer bandwidth and speed of Disk I/O is a massive win; in some cases it’s increased compile time by over 350% and made handling source repositories with 115k+ objects a joy. So much love for this SSD!

    BUT.. If you are based outside of the US and you have a problem you are in for a whole world of pain, even with the pro-active support from #OWC. My first Excelssior started giving me verify errors 3 weeks ago and I had to purchase DiskWarrior to bring the drive back – thankfully I had backups too.

    After some pushing OWC agreed to send me an advanced replacement, which despite being a “replacement” HMRC will charge you import duties against (£75); you must then claim them back through a C285 Reclaim Form. To do this effectively you must request entry forms from the courier (in my case UPS) for the original and replacement.

    To make matters worse UPS want an account payer *based in the US* to pay any charges (despite the fact there won’t be any as I’ve included evidence to a US company) and OWC won’t provide theirs, so currently I’m sat with a potentially faulty Excelssior under my desk with the likelihood OWC are going to charge me for the advanced replacement. Also UPS are quoting me £65 to return the SSD, which I won’t be able to claim back.

    Not Good!

  2. FYI;

    Since writing the original comment above OWC have been simply outstanding in not only ringing UPS and understanding the complexities I was eluding to above, but arranging to collect the item and provide necessary documentation.

    As the saying goes..
    “it’s never about the problem, it’s how it’s dealt with!”

    Thanks #OWC 🙂

    • Excellent; great to hear. OWC have super customer service and it’s great to hear that they went above and beyond on this, especially as DHL and duties aren’t really to do with their product range!

  3. Hi Ed – thanks for this post, it’s far and away the most useful I could find on this whole process. I’ve ordered one of these plus an SSD for one of my bays today, so looking forward to the speed boost… Just for info, the discount from Macupgrade is 5% not 10% now – still a discount, and still appreciated, just wanted to mention it. Thanks!


  4. Just a comment that I believe the OWC team have found and resolved the issue I was experiencing with Accelssior and OS X; this is their email which is worth taking note of:

    Greetings from OWC!

    We would like to inform you of the availability of a software driver for
    your Accelsior PCIe SSD.

    This driver is specifically for use with the Apple MacPro and OS X.

    Driver ensures proper power-down of Accelsior during sleep, restart, and
    shutdown actions that may otherwise not occur in the MacPro with PCIe
    connected drive volumes. This driver does not affect or interact with
    other drivers, software applications, hardware devices, etc.

    If you have not previously downloaded and installed this driver and you
    are using an OWC Mercury Accelsior PCIe SSD in a MacPro with OS X, we
    recommend you download and install this driver now:

    This driver is not required for use of Accelsior in Thunderbolt to PCIe
    Expansion chassis (such as OWC Helios). No driver is required for use of
    Accelsior for Windows or Linux operating systems.

    If you have any questions, our support team is here to help:
    800-275-4576 8AM to 10:30PM CT
    LiveChat 24/7

    Thank you

    – Team OWC

  5. Hi guys,

    great article, thanks.
    I plan to upgrade my 2009 MacPro with the just released With its simultaneous internal and external storage performance, the Mercury Accelsior_E2.
    I’m a big Aperture and Photoshop user with more than 2TB of Pictures on the hard drive.
    So my target configuration is have the system/application/user folders on the Mercury Accelsior_E2 and have the Picture folder on some couple 3TB hard configured RAID5 in the MacPro. I plan also to use the Apple fusion drive feature between the SSD and HD.
    Does someone have a similar experience? could you provide feedbacks?


    • Glad it was of use. Have no experience of the Fusion drive, but using the OWC Accelsior for OS and Apps is the way to do it, with data being kept on a different set of drives. In my setup, I have two further SSDs installed (in the optical bay; I now use an external optical drive which is only occasionally needed), one for my Aperture Library file and the other for Aperture’s referenced images; so the RAW files. Anything older than roughy six months resides on other internal hard drives. All of these regardless of where they reside, are backed up on RAID 1 drives off site and a RAID 5 drive (Sonnet Fusion D800) on site. As the SSD containing the referenced files gets near full, the oldest images are relocated using Aperture to one of the internal SATA HDs. I also have another on site drive where every assignment or shoot is backed up as an Aperture Project (Library – including the RAW files) – so there is a double backup strategy. As I use Aperture for not only photographs, but video and audio as well, all my multimedia content is managed and backed up in a similar way. My only advice to you would be to make sure you back everything up that’s on your RAID 5; don’t use that as the only location.

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