Vertex 3 slow write speed

Discussion in 'MacBook Pro' started by mangocheese, Nov 18, 2011.

  1. mangocheese macrumors newbie

    Nov 17, 2011
    I just got a 120 vertex 3, and my speeds are

    Read: Average 490 MB/s
    Write: 160 MB/s

    I used Blackmagicdesign Disk Test Speed to benchmark. I'm not sure why my read speeds are low. I put the ssd in the main drive, which is Sata 3 6 6bps. The ssd is also on firmware 2.15. Hopefully someone has a solution :confused:
  2. MoonshineSG macrumors member

    Aug 26, 2011
    prior to version 2.1 the test would show very high numbers.... Then....

    What's New in Version 2.1
    Some SSD's use hidden compression when writing data to make their benchmarked speeds appear faster. Disk Speed Test will now measure the true speed of these SSD's so you know if they are suitable for high quality uncompressed video capture.

    Last paragraph in the help says...

    "Important note about Solid State Disk (SSD) speeds

    Some models of SSD cannot save video data at the speed indicated by the manufacturer because the disk uses hidden data compression to reach these higher write speeds. This data compression technique can only save data at the manufacturer’s claimed speed when storing simple files or simple data, such as blank data. Video data includes video noise, and more random pixel data which does not compress much, so the true speed of the disk is seen.
    Some SSD’s can have up to 50% lower write speed than the manufacturer’s claimed speed, so even though the disk specifications claim an SSD is fast enough to handle video, in reality the disk is not fast enough for real time video data capture. Hidden data compression mostly affects capture and often these disks can still be used for real time playback.
    Use Blackmagic Disk Speed Test to measure accurately if your SSD will be able to handle uncompressed video capture and playback. Blackmagic Disk Speed Test uses data to simulate the storage of video so you get results similar to what you will see when capturing video to a disk. This will let you find models of SSD that work well for video capture. In our testing, we have found larger newer models of SSD, and larger capacity SSD’s are generally faster. Blackmagic Disk Speed Test also tests the speed of disks connected to eSATA docks and other interfaces, which can affect disk performance."

    Testing my Vertex 3 with pre 2.1 version


    and with 2.1


    Same SSD, 2 very different results. There is absolutely no change in the MBP speed.. (still boots up in 20+ seconds)
  3. mangocheese thread starter macrumors newbie

    Nov 17, 2011
    Thanks for the informative reply! It's good to hear that my setup is ok.
  4. dusk007 macrumors 68040


    Dec 5, 2009
    It is as fast as it is supposed to be. Smaller drives (240GB is almost twice as fast in write speed) are bad in write speeds & Sandforce are worse at incompressible data.
    If you check here.
    The AS SSD bench is with compressed data.

    For normal OS workload and installing apps it makes little difference and the Sandforce is actually better. For copying movies and big rar files around it is bad and the non Sandforce drives have the edge. For a lack of any source/target to copy the big compressed files too the latter is today usually not a limiting factor.

Share This Page