Performance difference between 512 and 1 TB flash drive in iMac?

Discussion in 'iMac' started by badlydrawnboy, Oct 22, 2014.

  1. badlydrawnboy macrumors 65816

    Oct 20, 2003
    I'm debating on whether to get a 512 GB or 1 TB internal flash drive with the retina iMac I'm about to order.

    I'm going to hook it up to a Thunderbay IV with plenty of storage, so I don't think I need the full 1 TB for the internal drive (since I will only ever have OS X and apps on it).

    But if the 1 TB drive is significantly faster than the 512 GB, I might consider it. This stuff gets expensive, so want to be smart about where I spend my upgrade $$.
  2. badlydrawnboy thread starter macrumors 65816

    Oct 20, 2003
    Found something that answered my own question:

    Looks like the performance difference between the 256/512/1 TB flash drives is negligible, except in the case of small random writes, where the 512/1TB outperform the 256 (but not much difference between 512/1TB).
  3. infantrytrophy macrumors regular

    Oct 27, 2013
    I don't remember all of the details on this, but judging from research a few weeks ago it was widely accepted that the larger SSD drives were more efficient. I inferred that 512 GB was substantially better than 256 GB, and 1 TB moderately better than 512 GB.

    Apparently memory is lost in SSDs as data is repeatedly stored and retrieved. A service named "TRIM" recovers this "lost" memory. All SSDs are set up to leave a certain amount of memory unused, to assist in this housekeeping-like activity.

    The larger the drive is, the better, at least in this context meaning small amounts of memory capacity loss over time. I don't think that this implies that the larger drive would necessarily be faster, though.

    My take was that to the extent reasonable, go for the largest SSD drive that fits your budget.
  4. hyune83 macrumors member

    Sep 19, 2008
    Seems the money would be better spent for an external? A 512gb ssd is like $250-300 these days?
  5. tillsbury macrumors 65816

    Dec 24, 2007
    That's on the 2013 models. rMBPs have changed since then, and the iMacs could be similar.
  6. badlydrawnboy thread starter macrumors 65816

    Oct 20, 2003
    According to this post on Barefeats, the iMac flash storage did not get faster like the rMBPs. Is that what you meant?
  7. theSeb macrumors 604


    Aug 10, 2010
    Poole, England
    Yup, that is what he is referring to. On the latest rMBPs that 1 GB flash drive is faster than the smaller capacities. It seems like that this isn't the case with the riMac.
  8. Gary Irwin macrumors member

    Sep 23, 2011
    Comparing notes with an on-line Apple sales rep yesterday, he suggested instead of buying the 1TB SSD, the best overall solution in terms of cost/performance is to configure a new riMac with 512 SSD and put the savings from the 1TB SSD into an external Thunderbolt 2 RAID box...which together is faster than any internal storage solution Apple offers.

    FWIW I went with the 1TB SSD anyway becuse it's an elegant solution that will handle all of my data for the foreseeable future.
  9. badlydrawnboy thread starter macrumors 65816

    Oct 20, 2003
    Yep, that's exactly what I ended up doing. I ordered the 512 GB internal flash, then got a Thunderbay IV (with TB 2) with 2x 1 TB SSDs which I will put in a RAID-0. I think that will be faster than the internal storage, and the cost of the two 1 TB SSDs was only a bit more than getting the 1 TB internal flash drive.
  10. Bryan Bowler macrumors 68040

    Sep 27, 2008
    That's actually very good advice. For $500 (the cost of upgrading from an Apple 512 GB SSD to an Apple 1 TB SSD), you can buy an OWC Thunderbay 4 RAID 5 box and then add your own hard drives. Sure, you'll spend additional money on 4 spinning hard drives, but you'll have tons more storage room, practically the same speed, and redundancy too.

  11. badlydrawnboy thread starter macrumors 65816

    Oct 20, 2003
    According to this post by Digilloyd, seems Apple may have purposely limited performance of the iMac flash storage to differentiate the Mac Pro.

    I don't see any other reason why the flash drive in the iMac would be slower than the ones in the new rMBP and Mac Pro.
  12. Cape Dave macrumors 68000

    Nov 16, 2012
    Ouch. Of all the complaints against Apple for perceived slights, I find this one horrific.

    That just makes no sense to me at all.
  13. badlydrawnboy thread starter macrumors 65816

    Oct 20, 2003
    I guess there's always a possibility a firmware update could fix it in the future, but I could definitely see Apple doing this.

    We're already seeing tests showing that the retina iMac is faster than the low end Mac Pro in many tasks. If the storage was just as fast, I could see a lot of graphics/video pros just going with the iMac to get the 5k screen.
  14. badlydrawnboy thread starter macrumors 65816

    Oct 20, 2003
    Barefeats just did more testing, and they found the same result.

    Granted, read/write speed of 760 MB/s is nothing to sneeze at, but it is disappointing that they didn't match the speed of the rMBP and Mac Pro.

    That said, as Barefeats pointed out, those who need >1,000 MB/s can attach an external device to get those speeds.
  15. shokunin macrumors regular

    Jun 7, 2005
    One possible reason is the number of PCIe Lanes available off the Intel PCH. If it's typical 8x PCIe 2.0 lane PCH, it might be divided as follow:

    1 PCIe Lane = GigE
    1 PCIe Lane = 802.11ac
    4xPCIe Lanes = 1 for each USB 3.0 port (4 ports)
    2x (what's left) = 2x dual PCIe for SSD

    rMBP has only 2 USB ports and no GigE allowing extra lanes to dedicate 4x to the SSD.

    TB2 is straight off the CPU so that wouldn't affect the PCIe lane count.
  16. badlydrawnboy thread starter macrumors 65816

    Oct 20, 2003
    Ah, someone who knows a lot more than me about this! That makes sense.
  17. Mac, M.D. macrumors newbie

    Oct 23, 2014
    I also went with the 1 TB SSD (changed order from 3 TB Fusion). I figure the SSD is something you can't really upgrade in the future. You can always add on an external HD for storing files other than OS, programs, etc.
  18. shokunin macrumors regular

    Jun 7, 2005
    I forgot the iMac also has a SATA III port the HDD, so the USB ports are probably not dedicated for each port. There might be a hub in there to split the bandwidth between the USB ports.
  19. Cape Dave macrumors 68000

    Nov 16, 2012
    Yes! Smart move!
  20. xgman, Oct 24, 2014
    Last edited: Oct 24, 2014

    xgman macrumors 601


    Aug 6, 2007
    Clearly seems to be the case. I guess it makes sense from their perspective ...
    Is there a comparison of how these new SSD's compare to the 2012 and 2013 imac ssd's?
  21. badlydrawnboy thread starter macrumors 65816

    Oct 20, 2003
    yes, here it is.

    they're almost identical to 2013, which was significantly faster than 2012

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