I am backing up my hdd with the Time machine. Even small incremental backups take several hours. For an hour or so I am in the state "50.3 MB of 496.3MB", while in Activity Monitor I notice that mds_stores has accumulated already over 116 GB data read, and it increases by about 50 MB/s. My Hdd is this new pcie-sdd type, so it should be efficient with this sort of backup. Moreover in Console it is written that about 2300 files constitute this 0.5 GB of backup.

I am backing up to external usb Toshiba drive.

Am I missing something obvious? This is not normal, is it? Can I see which of these 2300 files the Time machine is currently backing up? The "preparing" phase was not so long - took about 30 minutes.

  • Mine was a very similar question, with no solution, yet. apple.stackexchange.com/questions/244117/… Commented Jul 23, 2016 at 12:37
  • Indeed. I am consufed as number of files to copy is low, and these are small files. I do not see any regularities- sometimes backups are slow, sometimes they are quick, and this is not just a function of data size. I have restarted Spotlight, but ultimately leaving the computer for whole day and night was the only solution.
    – user68358
    Commented Jul 23, 2016 at 14:27
  • My OS drive (I have a MacPro with multiple drives) only has 50GB used. I just left for a few hours, after turning off Dropbox and PogoPlug. The current backup shows 1.17GB. No idea why this much data think it changed. Commented Jul 23, 2016 at 17:15
  • @Lacek How did you achieve reducing it to .5 GB? I am excluding almost every folder including hidden one yet it shows 15 GB.
    – vkg
    Commented May 22, 2020 at 3:10
  • I mean incremental backup, when the computer is untouched. Then the backup size is approx 460MB in my case. I did nothing to achieve that, it just is. At the same time I have lots of apps installed, but if they are not actively used I suppose their files are unchanged.
    – user68358
    Commented May 28, 2020 at 10:51

2 Answers 2


I was having the same problem pretty regularly. I tried the usual tricks (stop backup, eject, mount, delete .inProgress files, stopping spotlight, changing the throttle priority (sudo sysctl debug.lowpri_throttle_enabled=0). Sometimes, this works. Other times it doesn't and it keeps crawling along at a few MB per hour.

One additional trick, that works more frequently, is to force quit the backupd process directly from the Disk tab of Activity Monitor. Then tell it to start backup. This usually works for me. Heads up: this may be a terrible idea in other ways (e.g. maybe it could damage existing backups). In my experience, it hasn't so far.


In addition to setting sudo sysctl debug.lowpri_throttle_enabled=0, I've found Sophos can make backups really slow. I expect other virus scanners may have similar issues.

I found if I turn Sophos off I can make a backup complete in a reasonable time. Unfortunately we are required to use a virus scanner where I work as part of company policy, so I can't turn it off completely or remove it, only suspend it for 4 hours at a time.

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