Problems with Mac Mini 2018 and External HDD transfer speeds?

Discussion in 'Mac mini' started by Jenzbullets, Apr 23, 2019.

  1. Jenzbullets macrumors newbie

    Oct 4, 2018
    Hi, I recently moved to a 2018 Mac Mini (i7, 16GB Ram, 512GB SSD) from an i7 iMac late 2012.

    I am experiencing extremely slow file transfers on my external attached Hard Drives. Previously on my iMac everything felt fast and efficient. However on the Mac Mini its not so.

    I have 2 WD Ultra Portable HDD's connected via USB 3.0 on my CalDigit TS3+. The TS3+ is connected via Thunderbolt 3.

    I have a 4TB WD My Book connected direct to the Mac Mini's 3.0 port. I have a 4TB WD Passport connected via USB 3.1 and a Samsung T5 connected via USB-C.

    Copying a 3.2GB file from the 4TB My Book to the 4TB Passport takes over 10 minutes.

    Same file copied between the T5 and the internal SSD and vice versa takes 5 secs. The file from the T5 to the Ultras takes less than a minute.

    I would expect the file to take no more than 2-3 minutes to transfer via USB 3 to between the two 4TB drives, not over 10?

    Any ideas?
  2. treekram macrumors 68000

    Nov 9, 2015
    Honolulu HI
    You need to try different things to try to isolate the problem.

    Have you tried the 2 HDD's on another Mac? If it's slow there, it's likely a problem in one (or both) of the drives.

    See if 3rd-party background programs are causing the problem. Use safe mode to do this.

    Disconnect all USB-C (including the Thunderbolt dock) and USB-A devices except your keyboard and the 2 HDD's. Retry the copy. Then if it's still slow, try connecting the drives to two completely different ports.

    Make sure you're not running any other programs (except the Finder) when you're testing.

    If the condition still exists, it could be something with the file itself that's causing the problem (that would be strange, but who knows). You can create a test file and try copying that.
  3. Fishrrman macrumors P6


    Feb 20, 2009
    Disconnect EVERYTHING from the back of the Mini.

    Then connect the two "problem drives" DIRECTLY to the back of the Mini.

    Try copying NOW.

    What speeds do you see?

    If the speeds are still "slow", I'd look at the cables.
  4. Jenzbullets thread starter macrumors newbie

    Oct 4, 2018
    So I disconnected everything except the two drives (My Book ExFat via USB 3.0 and Passport Ultra AFPS) and problem still remained.

    I copied off all the data from the 4TB Passport Ultra and reformatted it as HFS+ (it was AFPS). Also did a full drive check on both drives with WD Drive Utilities and Apples Disk Utility.

    Low and behold now the file transfers between the drives are at the much, much higher speeds where the 3 to 4GB files are transferring in less than a minute.

    I have no idea what the issue was but definitely points to AFPS.
  5. Fishrrman macrumors P6


    Feb 20, 2009
    "I have no idea what the issue was but definitely points to AFPS."

    I previously recall reading (sorry, don't have a reference URL) that APFS can be problematical with platter-based hard drives. Something about file fragments and writes/rewrites all over the place.

    I see no reason to use it ... not yet.

    ALL my drives remain at HFS+ (including the INTERNAL drive in my 2018 Mini).

    The one exception is an APFS "mule drive" that I will use to obtain Mojave updates (as software update doesn't work properly with HFS+).
  6. treekram, Apr 25, 2019
    Last edited: Apr 25, 2019

    treekram macrumors 68000

    Nov 9, 2015
    Honolulu HI
    I have an external 1TB HDD that had HFS+ and ExFAT partitions that I was going to re-partition to a single HFS+ so I had it go on a detour to APFS.

    So I have 3 drives for this test.
    Drive 1: 8TB 3.5" Seagate HFS+ (used for the origin file - a 4.8 GB movie file).
    Drive 2: 1TB 2.5" Seagate 5400 rpm (HFS+ & ExFAT, then APFS, then HFS+)
    Drive 3: 500MB 2.5" Seagate 7200 rpm (ExFAT)
    All three are connected to the same USB hub. The 8TB is an external disk, the other 2 drives are bare drives in a USB enclosure. All destination HFS+ partition/drives were empty. The APFS drive was empty. The ExFAT drives had 200GB of data on it.

    Copying the same 4.8 GB file took:
    1TB drive, HFS+ partition: 52 sec.
    1TB drive, ExFAT partition: 78 sec.
    500MB drive (ExFAT): 42 sec.
    1TB drive, APFS: 47 sec.
    1TB drive, HFS+: 46 sec.

    So it may be that your HDD (one or both) were heavily fragmented and APFS doesn't handle HDD fragmentation well. Setting up a heavily fragmented disk wouldn't be easy to do unless you already have a script or better yet, a heavily fragmented drive that has been imaged. Or there could be something going on with your drives.
  7. harriska2 macrumors 6502a


    Mar 16, 2011
    Oops. I have 2 external 10tb drives and formatted one as APFS for my main data and the other Journal blah blah blah for Time Machine. Haven't had a problem. Will it cause early failure in the long run?
  8. treekram macrumors 68000

    Nov 9, 2015
    Honolulu HI
    Good question - which is better for HDD longevity: HFS+ or APFS? I don't know if there's any clear answer because Apple hasn't shared many technical details on APFS. I am not aware of anybody (credible) who has performed a test on this and really, the methodology of the test will have a major impact on the results (I suspect).

    One thing I have seen several times is that people believe the "copy-on-write" feature of APFS could cause major fragmentation on a HDD, resulting in reduced performance and likely reduced longevity. The copy-on-write features would typically be triggered when a file is edited. So say you use your HDD to store media files and you copy the files, delete them when they're no longer useful and then copy new media files on it. Then, copy-on-write shouldn't be triggered. But if you have many text files, spreadsheet files, possibly media files that are edited on the HDD, then copy-on-write will likely happen. It's also unknown whether APFS will defragment the files on a HDD behind-the-scenes. So one would need to make a judgement on whether or not it's worth the trouble to convert a HDD back to HFS+. Certainly, HFS+ is a known quantity and many of us plan on keeping HDD's on HFS+.

    This may also apply to the OP and possibly why there was a performance issue.
  9. Jenzbullets thread starter macrumors newbie

    Oct 4, 2018
    Just reporting back that after changing the one drive back from APFS everything is running far faster between these drives. Thererfore I am going to stay with HFS+ on my mech drives.

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8 April 23, 2019