SSD speed

Discussion in 'Mac Pro' started by Ed Miliband, Sep 1, 2014.

  1. Ed Miliband macrumors member

    Aug 27, 2014
    I saw that a higher capacity SSD is faster than a lower capacity one

    I have some questions

    - what is the speed difference and is it noticeable during normal use, or only when copying large files?

    - is it worth upgrading capacity just for this speed difference?
    - in other words will paying $x for a 512GB SSD give similar speed boost to paying $x (same amount) for 0.3Ghz more processor, for example

    - i read something about the 256GB PCIe-SSD having 2 lanes and the 512GB one having 4 lanes. what does this mean and how does it affect performance?



    sorry for not mentioning, i am talking about the new Mac Pro, and the Apple (preconfigured) SSD

  2. VirtualRain macrumors 603


    Aug 1, 2008
    Vancouver, BC
    Vendors that offer SSDs of different capacities often simply remove NAND chips from their reference design for the lower capacity models. Thus a 128GB SSD might have half the NAND chips that a 256GB SSD has. This often translates into less performance because the more NAND chips an SSD has, the more I/O operations that can be done in parallel.

    Like you say, some larger SSDs will typically have 8 or more NAND chips (thus 8+ channels) in parallel... smaller ones might have as few as 4 or 2. Not all SSDs are made like this, but many are. And chances are, if you see different read/write performance specs for different capacity drives, this is exactly why.

    Some SSD manufacturers offer the same performance in multiple capacities by using the same number of NAND chips but with each NAND chip having different capacity. This is the preferred way to do it of course, but it's more expensive because of the number of parts and slightly increased complexity in manufacturing.

    I wouldn't buy a bigger SSD than you need just for a bit of added performance... chances are you will never notice it. I would buy a bigger SSD than you need because you invariably need more storage and it will cost you more in the long run to incrementally upgrade every time you fill up the drive rather than buying a much bigger drive in the first place.

    When it comes to the SSD in the nMP, I wouldn't worry about the speed - all of the capacities perform extremely well (with perhaps an advantage going to the 1TB model). However, I would definitely buy as big as you can afford and then do some pan-handling or get a second job :p to buy one size larger than that because we just don't know if it's ever going to be easily upgraded, and you simply cannot duplicate the performance externally for less than Apple charges for upgrades to the internal SSD.

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