MBP 2TB Hard Drive Cache

Discussion in 'MacBook Pro' started by jblagden, May 2, 2016.

  1. jblagden macrumors 65816

    jblagden

    Joined:
    Aug 16, 2013
    #1
    I’m thinking about taking out my MacBook Pro’s optical drive and replacing it with a 2 TB hard drive. I checked out some hard drives and I noticed that Seagate has two drives which are very similar and the only difference between them is that one has a 32 megabyte cache while the other one has a 128 megabyte cache. I’ve noticed that if I’m watching a movie in the backseat of a moving car and the car hits a bump in the road, the stock 5400 RPM hard drive would stop playback momentarily as the read/write head needs to find the spot where it left off. Would a 128 megabyte cache help avoid that problem? Or is a 32 megabyte cache sufficient? By the way, I discovered that the stock drive has an 8 MB cache.
     
  2. JTToft macrumors 68040

    Joined:
    Apr 27, 2010
    Location:
    Aarhus, Denmark
    #2
    I have no comment on the cache thing, but I just want to mention that it if the drives you're looking at are SATA III, there's a chance they won't work in the optical bay of your machine (provided we're talking about the one in your signature). 2011s are known to be hit or miss with SATA III stability in the optical bay, though there's some data to suggest the 13" is less affected than the larger models for whatever reason.
     
  3. jblagden thread starter macrumors 65816

    jblagden

    Joined:
    Aug 16, 2013
    #3
    Yeah, I’ve heard about that. I’m not too concerned about that because the 2 TB drive will just be for media. I’m booting from a 480 gigabyte Solid State Drive which is in the hard drive bay.
     
  4. JTToft macrumors 68040

    Joined:
    Apr 27, 2010
    Location:
    Aarhus, Denmark
    #4
    - The issue applies no matter what data you store on it. Symptoms can be random unmounts, failed data transfers, even data corruption.

    For what it's worth, my 2011 works with a SATA III SSD in the optical bay, but others behave bizarrely.
     
  5. jblagden thread starter macrumors 65816

    jblagden

    Joined:
    Aug 16, 2013
    #5
    Oh, okay.

    Is that a 13 inch MacBook Pro?
     
  6. JTToft macrumors 68040

    Joined:
    Apr 27, 2010
    Location:
    Aarhus, Denmark
    #6
    - No, 15" as per my signature.
     
  7. jblagden thread starter macrumors 65816

    jblagden

    Joined:
    Aug 16, 2013
    #7
    Interesting.
     
  8. duervo, May 2, 2016
    Last edited: May 2, 2016

    duervo macrumors 68000

    duervo

    Joined:
    Feb 5, 2011
    #8
    It depends. The cache would have to be large enough to hold the entire file that you would be playing in order to make a difference.

    Are your files less than 32MB? If so, then the 32MB cache may help.

    Are your files greater than 32MB, and less than 128MB? If so, then the 128MB cache may help.

    Even then, you don't have any control over what data gets cached. It's determined by fancy algorithms programmed by the manufacturer. Generally, the most requested data will get cached first. For anything that will only be requested once in a blue moon, it may not be cached, regardless of how small it is. So, chances of skips will be minimized somewhat at best, but never guaranteed.

    If they are larger than 128MB, then it won't make any difference.

    If pauses due to bumps are that important to you ... More important than cost specifically ... then get the largest 2.5" SSD that you can. Not for performance, but for its lack of moving parts. No moving parts means no chance of drive pauses or skips due to bumps.
     

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