Blackmagic Disk Speed Test showing slower results

We have been installing a new Xsan system the latest days (more about that in a later post). When testing the performance we use two different tools, and they have very different results, 186 MB/second vs 136 MB/second.

The first one is Xsan tuner, that comes with Xsan:

Xsan tuner

Speed is calculated to 186 MB/second.

We use DeckLink Extreme HD cards in the Macs (10 bits uncompressed SDI). Blackmagic also has their own test tool for disk speeds, the Blackmagic Disk Speed Test:

BlackMagic Disk Speed Test

Now, the same disks show 136 MB/second.

Which one to trust? BlackMagic make dead solid products, but on this one I hope their tools show the wrong results…

If you need to test your drives for speed, whether you use BlackMagic cards or not, download the DeckLink drivers for Mac OS X or Windows XP, and you’ll get the Blackmagic Disk Speed Test application when you install it. If you don’t need the actual drivers, just “hide away” the app, and uninstall the drivers again.

Xsan tuner can be downloaded from Apple.com.

Why a difference?

Do you have any idea why the two apps show different speeds? 136 MB/second up to 186 MB/second is almost two more streams of uncompressed video in realtime. Less rendering, more done.

  • Kristian

    Coincidentally, I subscribe to your feed. Here’s something I pulled from one of our tech notes why this is so:

    “We recommend testing your disk array with Blackmagic Disk Speed Test as many other disk utilities do not take in to account factors such as the RAM cache which may be used in some disk arrays. Blackmagic Disk Speed Test can be used on any Mac or PC which has a DeckLink card.”

    http://www.blackmagic-design.com/support/detail.asp?techID=61

  • Kristian

    Coincidentally, I subscribe to your feed. Here’s something I pulled from one of our tech notes why this is so:

    “We recommend testing your disk array with Blackmagic Disk Speed Test as many other disk utilities do not take in to account factors such as the RAM cache which may be used in some disk arrays. Blackmagic Disk Speed Test can be used on any Mac or PC which has a DeckLink card.”

    http://www.blackmagic-design.com/support/detail.asp?techID=61

  • http://www.brilliantdays.com Oyvind

    Thanks Kristian! I’m reading this as “Blackmagic Disk Speed Test gives a better and more realistic result than Xsan tuner”… ;-)

    We get 9 streams of uncompressed 10-bit from the SAN. How does that relate to the numbers the two different tools show?

  • http://www.brilliantdays.com Oyvind

    Thanks Kristian! I’m reading this as “Blackmagic Disk Speed Test gives a better and more realistic result than Xsan tuner”… ;-)

    We get 9 streams of uncompressed 10-bit from the SAN. How does that relate to the numbers the two different tools show?

  • Kristian

    Are all nice streams visible in your timeline? This is the main question.9 streams don’t seem to match what your Disk Speed Test results.

  • Kristian

    Sorry, what I mean is if they are visible and playback in your preview window.

  • Kristian

    Are all nice streams visible in your timeline? This is the main question.9 streams don’t seem to match what your Disk Speed Test results.

  • Kristian

    Sorry, what I mean is if they are visible and playback in your preview window.

  • http://www.brilliantdays.com Oyvind

    We didn’t test 9 streams on one Mac. We put up two on each and started 5 Macs. The last one got dropped frames. When we switched to one stream on the last Mac, they all played for hours without stopping.

  • http://www.brilliantdays.com Oyvind

    We didn’t test 9 streams on one Mac. We put up two on each and started 5 Macs. The last one got dropped frames. When we switched to one stream on the last Mac, they all played for hours without stopping.

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