Time Machine Error - "The backup disk image could not be mounted"

This is mostly just my impressions, but I thought I would share them.

The update to 10.5.3 seems to be an improvement for my backups as well. Before, it would stop before completing especially on larger backups to the point where I felt like I had to do them over night via a wired connection. Also, time-capsule would alert me that the network connection was dropped and now I don't see that as much. We have a slower dsl setup, so that might be part of that, but with 10.5.3, both time-machine and my overall network seem to be working better.

You need to delete the sparse bundles and then restart the back ups. This same issue has happened to me with 3 of the 4 computers we backup with Time Machine/Time Capsule and is really getting a bit ridiculous. Apple "Genius" explained to me how to fix this issue when it arises but have not helped me find a permanent solution for this problem.

Go to finder and select the time capsule. Select the backup you are having problems with. Choose show contents and delete. Then restart the backups. Basically you have to start the back ups all over again.

I also suggest archiving your Time Capsule to an external hard drive monthly to make sure you do not loose any previously backed up data.

"deleting" the backup disk image and starting anew is not a solution, in my book. Sure it sounds easy and simple, but you forget that you lost your backup. What if the time your dmg failed you needed to restore an important file?
Consider this: A significant percentage of interrupted backups result in a corrupted disk image. Let's say that's 50% of the time. Time machine backs up every hour, and each backup lasts about 30-40 minutes. Let's say 30 minutes, a half hour. So half the time it's on, your machine is backing up–which means that if your hard drive fails, you have a 50% chance that you'll be backing up, thereby a 50% chance that you'll interrupt a backup in process (which has a 50% chance of corrupting your backup). I'm no statistician, but by my math if your had drive crashes, you have a 25% chance that your backup will be corrupt and unusable. That's one in four. If an office of 8 people gets a power surge and 8 internal drives get fried, 2 of those 8 people will have lost all their data, even though they were resting easy that Time Machine was happily backing up their files.

Backups need to be reliable. They don't need to be fast or fancy, they only need to be reliable. From my experience, and what I've read in this forum and other similar, Time Machine backups (at least over time capsule/airdisk) are not.
THis is not to say that network backups, even over WiFi, can't be reliable. I backed up for years over the network, wirelessly, using rsync. Once in a while I'd shut down in the middle of a backup and I'd end up with a corrupt file, but the rest of my files were still there and next time the backup ran I was back in business. I believe the issue here (and why I believe directly-connected/USB backups are more reliable) is that network backups using time machine use a disk image. When the disk image gets corrupted, you lose all the data stored therein, not just an individual file here and there.

i heard 10.5.3 has some fixes on time machine backups, but I have no details: I can only hope. And 10.5.4 is rumored to be out soon, but again I've no information on what's included. But for my money, this needs to be fixed asap.

Alvin Comiter1 wrote:
Every time I try I get a dialog box that says "Time Machine Error - The backup disk image could not be mounted."

SOLVED:
http://sudan.ubuntuforums.com/showthread.php?p=5212655

Looks like this may be a problem that occurs when a backup fails (or partially completes). Luckily, it's easy to fix. For completeness, here is a copy of the directions from the above link:

1) Connect to the shared drive from your Mac
2) Mount the .sparsebundle on your Mac
3) Inside the .sparsebundle, expand the folder "Backups.backupsdb"/<your username>
4) Sort the contents by date
5) Delete the link "Latest" and also the most recent incremental backup folder (ie. "2008-06-18-075750")
6) Unmount the .sparsebundle
7) Go into Time Machine Preferences, choose "Change Disk..."
8) Select the shared drive (not the sparsebundle)
9) Click Start Backup. After "Preparing" for a little while, it start backing up again.
10) Click Enter Time Machine when it's done backing up. All of your old backups should be visible (whew!)

Unfortunately, I appear to have a different problem (I found this thread via Google search, so apologies if it's old). When I attempt to follow those directions, Disk Image Mounter tells me that I cannot mount the disk because "no mountable file systems."

Any solutions for that problem, or do I have to delete and start over (again!).

jW

This solution appears to have fixed my problem. Thanks for sharing. This has been a very frustrating issue.

I am having the same problem. Has anyone else found a solution to this?

the above got me going in a constructive direction. i'm running current tc firmware and 10.5.6, but have had this same frustrating problem for several months. (TC worked great when new, and I think I lost ability to do b/u after os update).

Don't know how to "mount" sparse bundle, so simply tried to open, and got message saying it wouldn't mount. I then moved the offending sparse bundle to a subdirectory rather than deleting it and Time Machine spawned a new sparsebundle. progress. I managed then to get an out of space error, so now I'm deleting my hidden sparsebundle and starting again.

Apple: help us out here, there are clearly a number of us having very similar time capsule problems. my hardware and software are 100% apple.

WONDERFUL! Thankyou! Works PERFECTLY!!!!

I moved my Time Capsule disk to a different machine and ran into the error message above. Reading earlier responses to this discussion, I deleted the sparsebunde and everything now seems to be working fine. Thanks!