New 2017 MacBook - Slow SSD Read Speeds

Discussion in 'MacBook' started by MMcCraryNJ, May 2, 2018.

  1. MMcCraryNJ macrumors 6502

    Oct 18, 2012
    Hey all,

    I took advantage of Best Buy's one day sale on Monday and picked up a 2017 Retina MacBook, the mid-tier i5/8GB/512GB model. Been setting it up and such and decided to use both AJA Lite and BlackMagic to test the SSD. Both apps give me the following:
    Screen Shot 2018-05-03 at 12.44.30 AM.png Screen Shot 2018-05-03 at 12.45.30 AM.png

    Write speeds are where they should be but the Read speeds are nowhere near.

    FileVault is turned on and doesn't appear to be actively encrypting.

    Any ideas? Thank you!
  2. Mike Boreham, May 3, 2018
    Last edited: May 3, 2018

    Mike Boreham macrumors 65816

    Aug 10, 2006
    FileVault is almost certainly the cause. The Anandtech review of the 2016 MacBook includes this chart.

    Screen Shot 2018-05-03 at 08.08.21.png

    Read speed is reduced by 31% and write speed by 11%.

    I know the 2017 model has different faster storage but reductions will occur, but not necessarily the same percentages. I have seen quite wide range of reported results for the effect of Filevault, including larger reductions.

    On a SSD drive I don't think the effect is noticeable in ordinary use.

    Not sure I understand your comment that FileVault "doesn't appear to be actively encrypting". What are you expecting to see? Are you concerned that it is not encrypted?
  3. MMcCraryNJ thread starter macrumors 6502

    Oct 18, 2012
    Thank you for your response.

    The problem seems to be that SSD benchmarks are wildly inconsistent on my machine. If I let the test run for 3-5 minutes, I will get a couple of runs where the read speed jumps to 1200-1300 MB/S, but then cycles back down into the 300s again. In terms of real world performance, not sure if related, but sometimes simple apps will take 2-3 bounces on the dock before they open, ie Chrome. But after I exit it and reopen it, it opens instantly.

    So I'm not sure if my SSD is bugged out of box or if it's Filevault, but I've had both a 2013 Mac Pro and still have a 2012 MacBook Pro 15" with a Samsung 850 Pro drive in it, Filevault active, and I've never seen SSD benchmarks give this wild inconsistency.

    And by "Doesn't appear to be actively encrypting", I meant the progress bar in System Prefs had finished before I started to test the SSD speeds. So when you first set up a new Mac and put all of your files on it, there's a progress bar that says there's such and such time remaining before the contents of the drive are encrypted after you turn Filevault on. I let that progress bar finish before these tests.

    Can any other member here chime in?
  4. Neodym macrumors 68000


    Jul 5, 2002
    My apologies for reviving this old thread, but as the 2017 rMB is now available at more affordable prices, more user may face this problem:

    With my 2017 m3 I saw read speeds of ~350MB/s and write speeds of ~700MB/s with Blackmagic Disk Speed under High Sierra. I would have expected write speeds to take the bigger hit, but it seems that read speeds do suffer more (and significantly so).

    Turning off FileVault, write speeds went up to ~1.050MB/s and read speeds up to ~1.350MB/s. The test was far from being scientific or even running for a statistically relevant amount of time, but I think it gives a good ballpark impression.

    I’m not into the technical details, but - assuming the implementation is not flawed in general - reading & decrypting seems to take significantly more CPU power than writing & encrypting. And on the rMB macOS may be CPU-limited for that task. Unfortunately I have disabled FileVault already on the 2017, so I can’t look at the CPU load during testing, but there is an interesting side note: on the 2015 m5 with FileVault enabled, I get write speeds of ~350MB/s and read speeds of ~750MB/s.

    So roughly twice the read speeds with FileVault on the older machine with a (supposedly) slower SSD. Could it be that the m3 in the 2017 rMB is lacking some functionality which is present on the m5 from 2015 and that is relevant for FileVault speeds? Can anyone with a 2017 rMB and i5 or i7 run a BlackMagic test with FileVault enabled?
  5. sanchezfj macrumors newbie


    Feb 12, 2019
    Same here with an early 2016 Macbook Retina. I was not able to find any suitable explanation to this SSD speed results till I have read your post. Even Apple support was of no help with this. Thank you very much.

    I have FileVault active. I have just turned it off. I will test again when it finishes decryption, but I suppose what results I will get.

    Best regards.

    PS. Does anyone have a suitable cause for this results with FileVault turned on? Thanks in advance.
  6. sanchezfj macrumors newbie


    Feb 12, 2019
    I have just completed the test with FileVault turned off. As expected, results are now coherent (Write 842MB/s - Read 962MB/s). Perhaps this problem is related with the way BlackMagic makes this kind of test. I have also checked with Novabench and results are different but very similar with FileVault on and off. This seems to be more credible than BlackMagic results.
    Suggestions to solve this "mistery" are welcome!

    Best regards.
  7. cynics macrumors G4

    Jan 8, 2012
    How much free space does the SSD have?

    Blackmagic Disk Speed Test is not really a benchmarking program (at least not for raw HDD/SSD speeds). Blackmagic is a company that specializes in video editing software and hardware and their Disk Speed Test software is no different. It's specifically designed to tell you if your systems storage can play and capture uncompressed video using different resolutions, color depths, frame rates, and formats. It then reports them as FPS in the 'How Fast?' section.

    Since Blackmagic using a large temporary video file for its test you'll never get advertised speeds. Techniques like compression won't work very well. Plus its showing you sequential read/write which isn't very representative of real word use where you are using files of various sizes that are comprised various types of data. Also their test can be easily influenced by other processes (like video editing) which can lead to inconsistent results.

    Blackmagic says to expect up to a 50% reduction in its reported read/write speeds vs other benchmarks and manufacturer advertised speeds.

    I would recommend a benchmarking tool such as AmorphousDiskMark (there maybe better options out there) since it will give you data more toward what you are looking for in a format similar to CrystalDiskMark

    Here is a screenshot of both to highlight the difference.

    Screen Shot 2019-02-17 at 5.16.43 AM.png Screen Shot 2019-02-17 at 5.17.08 AM.png

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