With pre-release build 17A264c of 10.13 (macOS High Sierra) and 10.12.5 (Sierra) :

  • after five minutes' idle time, the throughput drops to less than 4 MB per second (data written, reported by Activity Monitor).

High Sierra:

Activity Monitor alongside the Security & Privacy pane of System Preferences

Later in the day, Sierra:

Activity Monitor

Touching a human input device (HID) – keyboard or trackball, for example – is enough to restore normal throughput, but it's potentially tedious.


Is there a technical explanation for the drop after five minutes?

I wonder whether it's an undocumented feature of firmware or Core Storage.

What might be done to automatically prevent the drop?

I imagine a periodic script. Maybe every four minutes and fifty seconds.


The Energy Saver pane of System Preferences contains nothing relevant.

I thought of ControlPlane. As far as I can tell, its evidence sources can not include idle time.

I experimented with Coca (http://coca.willemkempers.nl/) and Don't Sleep! – not expecting either application to prevent the drop in throughput (because I don't associate the drop with sleep, dimming or screen saving); neither application had the required effect.

iAway can respond to an away state with an AppleScript, but (above) I have no idea what type of script might effectively end that state.


With an ssh connection to the Mac I can monitor device I/O, for example:

iostat -dIw 5

– and re: https://apple.stackexchange.com/a/105056/8546 I can measure idle time, for example:

ioreg -c IOHIDSystem | awk '/HIDIdleTime/{print $NF/1000000000;exit}'

– but I have not yet found a way to restore normal throughput after a drop.



  • booted from an external hard disk drive, Seagate GoFlext Desk, limited (by the Mac) to USB 2.0
  • no battery
  • wired keyboard and trackball (the integral keyboard and trackpad ceased to work shortly after a repair under the MacBook Pro Repair Extension Program for Video Issues).

With the disk limited in that way: normal throughput, during reversion, peaks at around 15.3 MB per second.

sh-3.2$ date ; uptime ; sw_vers
Sat 10 Jun 2017 21:27:36 BST
21:27  up  2:37, 3 users, load averages: 0.65 0.40 0.39
ProductName:    Mac OS X
ProductVersion: 10.13
BuildVersion:   17A264c
sh-3.2$ diskutil coreStorage list
CoreStorage logical volume groups (1 found)
+-- Logical Volume Group 56A20D1F-0F2F-42B1-A74C-7672D0811DAC
    Name:         10.13
    Status:       Online
    Size:         665805369344 B (665.8 GB)
    Free Space:   1552384 B (1.6 MB)
    +-< Physical Volume 856F1697-0BC9-4690-82CC-7DA01634B6D8
    |   ----------------------------------------------------
    |   Index:    0
    |   Disk:     disk1s7
    |   Status:   Online
    |   Size:     665805369344 B (665.8 GB)
    +-> Logical Volume Family 98B2D42D-2B77-42B2-B176-243CAA4FA342
        Encryption Type:         AES-XTS
        Encryption Status:       Unlocked
        Conversion Status:       Converting (backward)
        Reversion State:         Reverting
        High Level Queries:      Not Fully Secure
        |                        Has Visible Users
        |                        Has Volume Key
        +-> Logical Volume 448EF942-2AFC-441F-83E0-C83A24EC2C56
            Disk:                  disk2
            Status:                Online
            Size (Total):          665451495424 B (665.5 GB)
            Conversion Progress:   61%
            Revertible:            Yes (unlock and decryption required)
            LV Name:               10.13
            Volume Name:           10.13
            Content Hint:          Apple_HFS
sh-3.2$ mount
/dev/disk2 on / (hfs, local, journaled)
devfs on /dev (devfs, local, nobrowse)
map -hosts on /net (autofs, nosuid, automounted, nobrowse)
map auto_home on /home (autofs, automounted, nobrowse)
sh-3.2$ diskutil list
/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *160.0 GB   disk0
   1:                        EFI NO NAME                 104.9 MB   disk0s1
   2: 516E7CBA-6ECF-11D6-8FF8-00022D09712B               155.6 GB   disk0s2
   3:               FreeBSD Swap                         4.3 GB     disk0s3

/dev/disk1 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *2.0 TB     disk1
   1:                        EFI EFI                     209.7 MB   disk1s1
   2:                  Apple_HFS 10.12.5                 249.3 GB   disk1s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk1s3
   4:                  Apple_HFS 10.9.5                  199.9 GB   disk1s4
   5:                 Apple_Boot Recovery HD             650.0 MB   disk1s5
   6:                  Apple_HFS Graham                  684.1 GB   disk1s6
   7:          Apple_CoreStorage 10.13                   665.8 GB   disk1s7
   8:                 Apple_Boot Recovery HD             650.0 MB   disk1s8

/dev/disk2 (external, virtual):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:                  Apple_HFS 10.13                  +665.5 GB   disk2
                                 Logical Volume on disk1s7


Screenshot of a System Information view of USB

  • 2
    It's a thankless task to answer your question considering the semi-broken MBP and a system/beta system on an external drive. 1st: I would try to attach the wired keyboard and trackball to the same USB-bus as the integral keyboard and trackpad and the USB-drive to the remaining free one. 2nd: what's the manufacturer and model of the external drive? – klanomath Jun 11 '17 at 20:39
  • Thanks. I edited the question to include drive hardware information, and a shot of System Information. From someone else's discussions.apple.com/thread/7846726 for a MacBookPro8,2 at first I assumed that if the integral keyboard and trackpad were found, with this Mac, they would be on the same bus as the built-in FaceTime HD camera. discussions.apple.com/thread/6809981 makes me assume the opposite so I'll shut down the Mac and put the drive on the other bus. Removal from Core Storage world completed, so it might be a while before I can reproduce the dropping environment. – Graham Perrin Jun 12 '17 at 3:47

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