I thought this thread had a solution for a problem I emailed you about in June of 2010 but I'm not sure that it is working properly.
My original problem was that I had to first use Finder to access the Time Capsule and then the external drive folder containing the sparse image to get SD to work. And often even that is not enough and I need to reboot the computer before I use the Finder trick. IF I don't the SD backup fails and I get the message: "failed to mount idisk backup".
I recently spent hours trying to teach myself automater to do the finder trick every night before backup time, but even though it would work if run manually, I could never get it to run as a ICal entry.
So I just found and tried the solution in this thread for my idisk backup which normally backs up in less than 1 minute. Now it takes over an hour. And in Finder I see an idisk backup.dmg file along with my idisk backup.sparseimage file. Fine, it worked. But when I repeated the backup it took another hour.
I saw that there was another forum thread about the sparseimage file being changed to a dmg file but that ended before any explanation as to what was happening.
So is my system supposed to create a dmg file each time and take an hour for each backup?
I just ran the idisk weekly the old way by just using COPY NOW and it worked perfectly (in 15 seconds) without the Finder trick. But that might be because SD just ran the 1 hour version of idisk backup so it already knows where the sparse image is located.
