ubd was eating up all network bandwidth after latest upgrade.

It synchronizes Mobile Documents with iCloud.

I'm also on Mountain Lion 10.8.2 and just added tethering to my mobile plan since wifi has been so poor at local restarurants. Turns out it was the ubd process pulling down 0.25 .. 0.5 MB/s for hours on end. It stops if I restart, but starts again if I open Numbers, Pages, or Mail. iTunes, Sarafi, iMessage, Calendar & Contacts seem to be safe. Even if I close those apps, it continues. Good thing I turned off the tethering when I noticed I wasn't able to listen to an audio stream without frequent interruptions. I checked my AT&T usage, and apparently I downloaded 200 MB of content during lunch today! If I had left it on all afternoon it would have blown through my entire monthly alotment of data. What is it downloading?

Linc has answered "what". I will say that it is a very bad idea to delete it! It makes the file synchronisation between your iDevice and your Mac happen. If there are large amounts of data in your Documents, then it could take a while to sync, but once done, it should settl edown.

I can't find any documents that aren't already synchronized. And besides, I only have 52 MB's in iCloud document storage total. And judging by the inspector in Activity Monitor, it isn't actually touching any document files. It keeps opening and closing Microsoft_Intermediate_Certificates and some file in Mobile Documents/.udb/peer-....../ftr/tmpm-..... I can't find any such file in Finder (I have in fact found the .../ftr/... directory). Anyway, every now and then I do see the iCloud version of an actual Pages document come through, but they're ones I haven't edited in months, and they only come once every few minutes or so. That's no excuse for the alternating 398 KB/s / 0 KB/s I'm seeing every other second right now.

LOL. You actually did that?

OK, well when none of your iCloud applications sync documents any more, you'll know why. If you want to fix it, you'll need to reinstall your OS.

Next time, try rm -rf /

If you want the synching to stop, then go to your iCloud account in System Preferences, and uncheck "Documents & Data."

You'll be asked to set a directory aside. Say OK. And then notice things like mail rules don't sync between machines, which is apparently OK.

I was given a link to this thread by an AppleCare representative.

I noticed that in the last few days we had been getting through significantly more data than normal - even overnight when the computers are relatively idle it was using about 7 GB.

I was able to log into my Draytek Vigor 2710 router and find out that it was the IP address of my Mac Pro that was using all the data.

Then I used Little Snitch Network Monitor to see what processes were using all the data. As mentioned above it was ubd - and more specifically it was 3 processes - p03-ubiquity.icloud.com, p03-content.icloud.com and another called something like blob. something .windows.net (apparently this is cloud storage used by iCloud).

Concurring with what was said above, I was told it was Documents and Data that seemed to be the problem. I signed out of iCloud and allowed it to delete everything from my Mac Pro, then signed in and restored everything except Documents and Data.

My plan is to see how things go without using iCloud Documents and Data - and if no further problems I'll try ticking that again and monitor it closely.

My suspicion is that some corruption occurred with iCloud documents or the sync process (second problem I've had with iCloud so far).

It's a shame because things like this NEVER seem to happen with Dropbox - even though I use Dropbox far more extensively and for far longer.

Just to add, in console Ubiquity, there was a log called ubiquity-digest.log and it contained

[13/02/02 15:04:41.926] disconnected from 'iCloud'

[13/02/02 15:04:41.927] there was a http error 503 while talking to iCloud reason: Throttled; try again later (Account)

[13/02/02 15:04:44.088] Requesting 4 item downloads from iCloud

and the last line was repeating constantly, with the other 2 lines about the disconnection showing periodically.

This has been happening constantly since 29th January 2013 (eg. the last 5 days). I estimate we have got through nearly 100GB of data as a result of this problem in the last 5 days.

Thank you for this thread and the replies. I've had the same problem for quite a few days now, with Little Snitch showing constant downloading by the ubd process (mainly the blob...core.windows.net server).

It's been hogging our network's bandwith nonstop – until I followed the above advice and unchecked Documents & Data in iCloud in System Preferences. It asked me to OK the deletion of iCloud documents from my Mac, which I did, then immediately the problem ceased. No need for a restart.

I made sure the problem apps Benjamin Spratling mentions above were quit, then turned on Documents & Data again, with no problem: the ubd process remained quiet. The apps he says are safe seem to be so on my system too. I tested a few more document-centric apps with iCloud support such as Notes, Text Edit, Preview and the third party app iA Writer, and these all initiated the same problem: as soon as the app is running and Documents & Data is checked, regardless of which comes first, the ubd bandwith hogging begins. Quiting the app does not solve this – only unchecking D & D does (or, according to Benjamin, a restart).

If someone hears of a fix for this before it comes in an update from Apple, I'd be grateful if you posted it here.

If turning off Documents and Data deletes the content from the Mac, I wonder if this effectively resets things. Therefore turning it back on might cause the process to restart because of downloading the files again - but perhaps given enough time it would complete this process and go idle again?

No, I don't think so. I don't have many files in iCloud in most of the apps I tested, and some have nearly zilch. Many are only text files, measured in the kilobits. And it doesn't explain Mail.app, which did not have its files deleted when I turned off Documents and Data, yet the ubd process still starts back up and goes on without end with just Mail open and none of the other offending apps. Preview too – there's nearly nothing in my Preview iCloud storage, yet once it starts on and on it goes.

Sorry – double post. I thought my above reply had been lost.

Message was edited by: stillripple

Whilst I don't make great use of iCloud, I decided I wasn't happy with just switching Documents and Data off, so I went through the arduous proces of cloning the drive (as a backup), format, clean install.

Everything is installed again and I'm looking at Little Snitch with minimal network activity. I'm sure the problem must be related to file corruption. If it was a bug I'd assume the problem would recur. I'll be keeping an eye on little snitch though...

Fascinating. I have suspected corruption on my rMBP for a few months, expecially since iTunes swapped the album artwork all around and gave some music artwork from a podcast. Oh yeah, and occasionally the entire machine throws garbage on the screen and crashes. I just assumed that a time machine back up would also save whatever caused the corruption in the first place. I guess it's good to hear that wasn't your experience. If the problem starts back up for you, please, please post here. Oh right, and just for clarification, how, exactly do I go about reinstallig Mountain Lion, cleanly? What if the copy on the recovery partition is faulty? Can I do this from another Mountain Lion machine? A link to some instructions would be greatly appreciated.