SSD = no need for more ram

Discussion in 'MacBook Pro' started by LyonParis, Dec 5, 2011.

  1. LyonParis macrumors newbie

    Dec 5, 2011
    I've read on a lot of SSD tests that these disks could "substitute" to RAM.
    As they have a latency time in micro-seconds (while HDD have it in milliseconds) they can expand RAM need with a widely acceptable performance loss ?

    What do you think of that ?
    Did you observe significant performance gain by adding more RAM memory with an SSD disk ?
    (if you confirm I could save some money to buy me a better SSD).
  2. maflynn Moderator


    Staff Member

    May 3, 2009
    No, you're mistaken.

    RAM is used by applications, while executing. Disk or SSD storage used to hold data.


    SSDs improve only disk or IO bound operations, more ram can possibly increase the performance by reducing the amount of swap outs to disk (or SSDs) that is its able to keep more memory pages in RAM instead of sending to the disk which is slower then RAM.
  3. Weaselboy Moderator


    Staff Member

    Jan 23, 2005
    I think what you are referring to is the fact that if you are short of RAM and this causes page in/out to the drive, these page in/out would be much faster on a SSD than a HDD. So if you have a machine that is short of RAM it would be much less noticeable on a SSD equipped machine.
  4. thundersteele macrumors 68030

    Oct 19, 2011
    It's true. When I run out of RAM with a HDD, the applications whose data gets swapped out to the HDD get incredibly slow and beachball a lot. With a SSD under the same conditions, the performance loss is hardly noticeable, at least for me.

    If you regularly run out of RAM, I would still upgrade it:

    - swapping adds read/write cycles to your SSD, which will make it wear out faster (maybe negligible, I don't know)
    - SSD storage is expensive, you don't want to reserve too much of it for a huge swap file
    - there still is some performance loss
  5. LyonParis thread starter macrumors newbie

    Dec 5, 2011
    Thanks for your replies. I got an explanation and a confirmation !
  6. RealEvil macrumors 6502

    Aug 5, 2007
    I can definitely vouch for an SSD improving Paging performance but it still doesn't compete with actual RAM.
    If I max out my Mac Mini with VMs to the point where it has to page a LOT, eventually OSX will die (within 20 mins the machine will lock up). Thats with a M4 256GB.
  7. mdma macrumors newbie

    Dec 6, 2011
    no ssd is a substitute for more ram. ideally you want both.
  8. theSeb macrumors 604


    Aug 10, 2010
    Poole, England
    1333 MHz RAM is around 20 times faster in read and write operations than the fastest 2.5" SSD.
  9. VMMan macrumors 6502a

    Mar 29, 2009
    If I had to choose between the following:

    1. MacBook Pro with 4 GB RAM + SSD vs 8 GB RAM + HDD

    ==> I would easily choose the 4 GB RAM + SSD.

    2. MacBook Pro with 1 GB RAM + SSD vs 16 GB RAM + HDD

    ==> I would choose the 16 GB RAM + HDD

    If you have anything near a "decent" amount of RAM, then an SSD is the way to go.

    If you're seriously deficient in RAM, then get more of the RAM.

    2x4GB DDR3 RAM is $20-35 nowadays anyways, and 2x8GB DDR3 is about $200...
  10. thundersteele macrumors 68030

    Oct 19, 2011
    8 GB RAM is sufficient for most users. That's about $40-$50.

    A SSD might make a machine that's low on RAM feel less limited by it's lack of RAM. Still, there is no reason to not upgrade to 8 GB... if you could afford the $2k+ for a MBP with SSD, the RAM upgrade shouldn't be a problem.

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