Previous 1 2 Next 17 Replies Latest reply: Nov 13, 2012 4:55 PM by RichardFromRouyn-Noranda
RichardFromRouyn-Noranda Level 1 Level 1

After the switch to Mountain Lion, the backup strategy I used for years no longer works. I have two iMacs at home, each with an external hard drive used for Time Machine backups. Each iMac backup locally to the external hard drive and remotely to the external drive of the other iMac. My network is wired through my router; all the devices use Gigabit Ethernet. Normally one of the external drives is kept out of the house.


Ten days ago I replaced one of the iMacs with a new one and I immediately installed Mountain Lion on it. After the complete installation of all my stuff on that new Mac, I updated my local backup and I erased the backup on the remote Mac (which was still on Lion) and created a new one; this took normal time, about 3 hours for 215 GB (1.2 GB/min). But when I went to update the backup of the other iMac remotely on the new one, it was very slow. I then erased that backup and began a new one. It was extremely slow (about 11 MB/min) and Time Machine said that it will take 5 days to complete the 65 GB backup (compare to the 3 hours for 215 GB above).


I thought that this could be caused by a bad interaction between Lion and its successor. So I upgraded the other iMac to Mountain Lion. After that, same problem: the local backup went normally but the remote backup was still very slow. And now the remote backup from my first iMac is also extremely slow on the Mountain Lion host. I erased that backup and tried to create a new one; this time it didn’t complete in 3 hours but Time Machine estimated that the 215 GB will be backed up in 15 days!


After that, I also tested the direct copy from a Mac to the other and concluded that all is normal on that side. The copy of a 2 GB folder containing 82 files took about 35 seconds.


So, my experience shows that

1. backing up from either Lion or Mountain Lion to a remote host that is NOT under Mountain Lion goes normally;

2. backing up from either Lion or Mountain Lion to a remote host that is under Mountain Lion is abnormally slow.


Do you share similar experience? Have you found some solution?


Hope Apple will address that issue real soon now!

iMac, OS X Mountain Lion
  • Stewart Carlsson Level 1 Level 1



    I have this problem too! 80 Gb to backup through network to my Mountain Lion server with attached external drive....6 DAYS!?!

  • RichardFromRouyn-Noranda Level 1 Level 1

    Another Mac user reported the same experience and the same problem ( -lion/). From his experience, he pretends that Apple intentionaly slowed downTime Machine backup on remote host in Mountain Lion to promote use of OS X Server.

  • David Deininger Level 1 Level 1

    This matches my experience exactly.  I can also confirm that buying and installing Server does cause the backup speed to return to normal, but I don't think this (the slowness) is intentional on Apple's part, I expect a 10.8.x patch will address whatever is causing the problem.

  • Brandt Kurowski Level 1 Level 1

    I was suspicious that installing Server would fix this, but after the 10.8.1 update didn't change anything I decided to try.


    Before installing Server, Time Machine was estimating it would take weeks to backup my 10.8.1 system to another 10.8.1 system over gigabit ethernet (though regular file transfers were fast as expected). After installing Server and enabling Time Machine in the Server app, my Time Machine backups over the network are now back up to the same speed they were under 10.7.

  • Akitaguy Level 1 Level 1

    Same problem also, backing up to a SynologyNAS 212+,  normal file transfers are blazing fast. Created a new backup after reformated HD, currently backing up 241 GB and saying 2 days! It seems to be an issue with Mountain Lion as my old backup from Lion was running fine on the same SynologyNAS since March 2012.  Currently running OS X 10.8.1 on an iMac 27" i7 16 GB Memory.  The only change is partitioned 250 GB for Bootcamp and WIN 7 ( don't say it I know! )  Hope Apple is listening??

  • Stewart Carlsson Level 1 Level 1

    Problem solved! Installed OS X Server from App Store!

  • Akitaguy Level 1 Level 1

    My issues is also resolved, deleted the timemachine prefs created a new backup, completed 288 gb in just under 3hrs!

    (Synology DS212+). Works great again as before.

  • RichardFromRouyn-Noranda Level 1 Level 1

    But you don't had the exact same problem that I originally wrote about and that others experienced too. You had a problem backing up to a NAS from Mountain Lion. We have a problem backing up to a host running Mountain Lion (but no problem from Mountain Lion to a Lion host).

  • Barabas2005 Level 1 Level 1

    Experiencing the same thing here with OSX 10.8.2: Timemachine is extremely slow on my Mac Pro when using a drive on my Macbook Pro on the same network.


    I am using a programm called iStat Menus to track some of my machine's activities, so I decided to track the network activitiy as well during a Timemachine back-up session.


    My machines are connected to the network at 1000baseT speeds. However, when Timemachine starts on the Mac Pro the speeds are only around 80KB/s. While the back-up is still in progress, I switched to the WiFi network. All of a sudden the speed jumps to 5MB/s! When going back to the wired network connection, it even jumps to 30MB/s and the back-up finishes very quickly (like it always did before upgrading to Mountain Lion).


    However, when Timemachine starts its next session after an hour, it goes back to the very low 80KB/s speeds.


    It must be just a very simple setting in Timemachine that needs changing. Apparently this was done in the update for OSX 10.7.5, which also had Timemachine speed problems.

  • Jan Mostert Level 1 Level 1

    I have the same problem after upgrading my machines from 10.7.5 to 10.8.2. One iMac has an external HD that serves as backup destination for all computers. It is shared by the hosting iMac. Local TM backups are as fast as ever, but TM backups from other machines to this remote disk are very slow now.


    Yesterday I managed to get a fast backup on a macBook by following the instructions mentioned here:


    However, this is not what I want. I have to mount the external disk manually before running TM. Before TM mounted the disk itself.


    Something went wrong in Mountain Lion with Time Machine, for that I am sure. I really hope Apple did not do this on purpose. If so, I would be very disappointed.

  • Dimme Level 2 Level 2

    I am in the same boat. I am thinking of installing server app. Is that best the solution?

  • RichardFromRouyn-Noranda Level 1 Level 1

    Based on the experience of Brandt Kurowski and Stewart Carlsson reported above, I would say yes if the Mac is used only as a server or if it's not a problem for you working on a machine with server OS.


    On my side, I didn't have solved the problem yet. And I'm surprised that this have not been addressed by Apple yet.


    I don't want to use OS X Server on my machines wich are of day to day use. But I'm near of a solution: someone offered me a used Mac Mini; I will run this one as a server with Lion and I will plug the external drives on it. As a side benefit, I will have a server permanently available.

  • Brandt Kurowski Level 1 Level 1

    Installing Server seemed to fix the problem for me at first (before I installed Server, Time Machine was slow, after I installed it, speeds were reasonable), but sometime in the last few weeks things got slow again (without me having changed anything on the server). YMMV, but it no longer appears to be a silver bullet.


    Currently the only way I get decent throughput with Time Machine is to unplug my Ethernet and just use WiFi instead.

  • Dimme Level 2 Level 2

    I just installed server and started a fresh time machine backup. Looks like it going pretty fast. Sayes it will be done in 2 hours, not 6 days like before. Before server it would take 20 minuntes before it would even start to copy(said prepairing) now it started right away.

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