A question for the hard drive experts...

Discussion in 'Mac Pro' started by CaptainChunk, Jul 27, 2010.

  1. CaptainChunk macrumors 68020

    CaptainChunk

    Joined:
    Apr 16, 2008
    Location:
    Phoenix, AZ
    #1
    I ordered some hard drives for an upcoming low-budget short film the other day. Due to budget constraints I couldn't exactly buy the "ideal" drives, but these will work fine nonetheless. I ended up with the following:

    • (2) WD Caviar Blue 500GB (WD5000AAKS) 7,200-rpm (for camera data capture; 1 primary and 1 backup)
    • (1) WD Caviar Black 640GB (WD6401AALS) 7,200-rpm (for editing and post)

    After unpacking the drives, I proceeded to run the AJA System Test on each drive to test the read/write speeds and noticed some interesting things. Being a nerd, I was simply curious. And just to preface, all three drives were blank and freshly formatted (Mac OS Extended), with no data previously written to them. Here's what I noticed:

    I ran the AJA Disk Read/Write test using a 4.0GB file size at the 1920x1080 10-bit video frame size - on all three drives.

    The two 500GB Caviar Blues both tested at around 130MB/sec (that's pretty fast), read and write. Just to be sure, I ran the test several times and consistently got the same results.

    But the 640GB Caviar Black didn't fare as well. That one consistently tested at around 103MB/sec. (still pretty fast for a single drive), read and write using the same testing parameters. But...really? The Blues are actually 21% faster? That's pretty significant.

    The only thing I can really gather regarding why this is actually the case would be somewhat anecdotal in nature: the 500GB Caviar Blues are noticeably lighter in mass, which may indicate these drives use fewer platters than the Caviar Black does. And fewer platters usually indicates higher aereal density, thus the faster transfer speeds.

    I made this post out of pure curiosity more than anything. Perhaps someone more versed in drive technology may be able to shed more light but I'm assuming my assumption with the number of platters is correct.
     
  2. Hellhammer Moderator

    Hellhammer

    Staff Member

    Joined:
    Dec 10, 2008
    Location:
    Finland
    #2
  3. cube Suspended

    Joined:
    May 10, 2004
    #3
    I think your Blue is 1x500GB platter, while your Black is 2x320GB platters. That should explain the speed difference.
     
  4. CaptainChunk thread starter macrumors 68020

    CaptainChunk

    Joined:
    Apr 16, 2008
    Location:
    Phoenix, AZ
    #4
    This is the older Caviar Black (32MB cache) I ended up with.

    The numbers I reported where simply the ones generated from the AJA benchmarks I ran - and naturally, I would expect minor variances between those numbers and what WD themselves spec the drives at.

    And that's sort of along the lines with what I've been assuming, as well.


    But, no biggie. These drives will do what I need them to do. I was more curious than anything else. Thanks for the comments!
     
  5. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #5
    To get a bit more specific, the platter density is different; 500GB/platter for the Caviar Blues, 333GB/platter for that model of Caviar Black.

    So for each rotation, the higher density can transfer more information.
     
  6. CaptainChunk thread starter macrumors 68020

    CaptainChunk

    Joined:
    Apr 16, 2008
    Location:
    Phoenix, AZ

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