I'm also seeing extremely slow Time Machine backups. I've only had my Mac for a week, and am using a USB2 hard drive for Time Machine.
The initial backup and every backup since has been super fast and the expected speed, however today I am trying to backup and it is backing up literally 1kb/minute with 4GB to go!
I have the same problem with a mac running Mountain Lion Server with TM backups to a Time Capsule.
36 days to go, for only 130 GB, ridiculous, indeed !!!
The good news is that its only on ONE server, my others are doing their TM backups to the same TC as expected, well one decided it needed to start a new sparseimage because it could not guarantee the safety of the backup ...
I must concur with Pete on this. My wife and I have identicial MBA (mid2011) with identical USB2.0 backup devices (make, model, and size). The only differences between our two systems is a few apps. I have Xcode installed; its a job thing. She has Pages for writing college papers.
But there is one more difference. I upgraded to ML; she did not. Her TM backups continue to finish in minutes, where mine took almost an entire day for its last incremental, not full. My MBA will no longer backup unless it is given at least eighteen hours just for incrementals. Checking the TM logs it has been this way since the day I upgradedt o ML and has never looked back.
People can banter back and forth about Wifi speeds to Time Capsules all the want, but in the end its just scrapping for something to occupy time. Occum's Razor is living well and large here: Time Machine isn't broken over Wifi; It's just plain broken period.
At this point I'm giving serious consideration to searching for a 10.7 thumb drive and wiping my system back to Lion. The sad thing is, I have friends at work that were skeptical when ML was released and advised me to wait until it had "cooked" out the infamous dot-0 bugs all-too common in new Apple OS drops. These are guys that have been Apple eggheads since MacOS 9 and earlier. I, being relatively new to Apple as my MBA is my first Apple comp, naievly chose to roll the dice.
I (and dare I say, most of the people here) came up snake-eyes on the come-out. Don't make the same mistake. Monitor this and wait until Apple fixes what they broke. It will save you a LOT of headache down the road.
And if you're "working fine" after your ML upgrade, thats great for you, but without specific knowledge of (a) why you are not afflicted by this problem and (b) why we are, you're literally doing nothing helpfull and instead rubbing salt in the wounds of those that are suffering with this, so kindly refrain from the "not true; works great for me" comments. Glad for you if it does, Got anything usefull to go with that? Yeah.
I think I found the most obvious reason why TM to TC backups are went so slow on Mountain Lion ...
At least when you are connected to a wireless lan.
I found the transmission speed (Transmit Rate), what was previous with Lion 270, dropped to as little as 12 or even less to 7 ... My MBP still at the same place !!! And only 3 meters from the physical location of my TC.
I connected my TC with a cat. 6 UTP cable, and the initial backup just lasted a few hours, as it should be.
You can check the Transmit Rate of your wifi network on a TC with holding the alt key and pressing on the menubar icon of the ariport.(WiFi).
So in my opinion Apple has to check and update some wireless drivers soon for ML.
And I won't recommend a downgrade to Lion, as ML is much, much better, once you mastered it.
While i believe there are wifi issues, i dont believe they are the cause of the backup slowness. My 2012 mbp was wifi connected at 450mb/s with web surfing working perfect. File transfers between mbp and 3tb time capsule working as expected, i stopped the time machine backup after 6 hours when it only backed up 176mb of 450mb.
If you are on mountain lion and use WiFi, you can go to www.speedtest.net and test your internet speed. If you get expected MPS download/upload speeds to the internet, then its not a "WiFi" issue as much as it may be a home networking issue. There are a number of home networking troubleshooting things to try and resolve the issue.
For instance, in this order, power cycle your network devices:
1) power off your MAC (and all other network hard drives)
2) power off your router/switch (if you use a Time Capsule - it should be powered off at this step)
3) power off your internet modem/gateway
4) wait 10-20 seconds
5) power back on your internet modem/gateway - wait until all lights are at their normal operational position
6) power back on your router/switch - wait until all lights are at their normal operational position
7) power back on your MAC
Sometimes the IP address just need to be refreshed by all devices because the lease/certificate gets corrupted or just plain messed up (yes, that is a technical term. )
This is obviously basic stuff... but my backups via gigabit ethernet to a Lacie NetworkMax were very slow after upgrading to Mountain Lion. This helped make it go much faster... even though my system was semi jacked up.
I am about to start my new Time Machine back up over again since I seem to be good after my reload a week ago.
I would like to follow up to all of your comments and responses to my orriginal post. This afternoon a senior tech adviser from Apple called me at home to ask questions about my problem with slow backups in Time Machine running Mountain Lion. He ran a number of diagnostics on my Mac Book Pro for their engineers to analyze. Apple is listening and working to resolve this issue. I am confident they will resolve this Problem for all Of us. Thanks for your support.
I'm having the same issue with very slow Time Machine backups. Had to connect Ethernet cable to finish the initial backup post-Mountain Lion upgrade, and incremental backups are painfully slow ever since, everything from finding the backup volume all the way through cleanup just grinds!
I'm backing up to a Time Capsule wirelessly, and transmission speeds show 6 to 13 when TM is backing up, but if I do a speedtest on the Internet (speakeasy) while the TM backup is still running, the speed immedialtely jumps to 245 during the test, then drops back down to pre-test levels. So the issue appears to be related to TM and wireless in my case, not wireless in general. I can't say for sure if TM was any faster over Ethernet cable, since I went to sleep....
Reformatting fixed my backup speed problems. Took about a day to recreate my mac pro backup (wired) about 400gb (with Backblaze running as well). Took about half a day to recreate my mac book pro backup (wireless) about 100 gb. Both backups now happen quickly incrementally.
Regrettably sometimes the backups still fail when both computers try to access the Time Machine (capsule, 2 TB) at once. For whatever reason, the first machine backing up seems to lock the capsule so the second can't access it.
This particular problem has plagued me through SL, Lion, and ML so I am not concerned. It is easily fixed by deselecting and reselecting the drive. I turn off backups on the laptop and then there is no clash. I do them when the pro is asleep or shut down.
Don't do this if your backup is valuable to you. There are definitely problems for many with this and I am hopeful Apple fixes it in the next ML update which should be in the next month or so based on history.
Hope this helps
I have a Mac Pro with TM backing up to one local network location (NAS) and two local drives. ALL of them are terribly slow. Backing up about 400 gig on a local internal drive takes 33 days. I left it running overnight and it had finished about 10 gigs. I could have backup running all the time and never finish (as it actually has for about a week now).
The problem is NOT with WiFi as I'm not using it at all. The internal hard drive backups were made on empty disks, so I don't see how formatting helps.
Worse yet, the whole machine becames very slow when backing up. Beach balls all over. When backup is cancelled, everything is fine. Console log shows nothing which seems relevant. Processor load is low. I have checked the S.M.A.R.T. status of the internal disks, no problem there.
So TM is seriously broken under ML. Now I hope I hadn't upgraded just yet.
A note for the interested: I did a complete clean reinstall of Mountain Lion on a different disk on the same machine. Tried Time Machine and everything was a blaze, no problems whatsoever.
I have NOT yet copied my home directory from the old disk to the new one. But it seems the sluggishness may be related to upgrading from Lion.
The machine feels a lot faster in other respects, too. So I guess it was time for a clean install anyway. I don't remember when I did it last, but I think it was in Snow Leopard times.
I am experiencing the same issue with the first Time Machine backup after ML upgrade on my 1 yr old MacBook Pro.
My backup device is an external drive and it has been swift in the past. Ihave allowed it to run for a whole day and it still did not complete.
This time around, it took 30 min to push 450MB out of 52GB to the external drive.
Then, 15min later, it says 2KB out of 52.3GB.
May be there is a stupid bug in status update for the Time Machine backup.
I pretty sure the external drive is good.
I've deleted the old backup and started a new full backup on the Time Capsule, in first instance there seems to be no improvement but after 1 hour the estimated time decreased to 4 days and after 2 hours it decreased to 3 days. I left the iMac going on for the night and next morning it needs another 12 hours. The following evening the backup has finished (I know now that the total time needed is approx 16 hours to backup 130 GB where my feeling says more than 30 hours). Apple called me yesterday and asked me to create some logs so they can investigate the problem (this is a very appreciated pro-active action). Will be continued.