Yes, as a single file. The local iDisk is stored as a sparsebundle file in your user directory:

//Library/FileSync//< .MobileMeusername>_iDisk.sparsebundle

The above file will be backed up by Time Machine just like any other. If you have a problem with your iDisk that is the file you’d restore.

I’ve been using MobileMe on and off since it was .Mac and even prior to that when it was known as iTools and I remember that I and many others decided that iDisk syncing wasn’t worth the risks. Hopefully it can be relied upon now but I’d advise against storing important documents only on the iDisk. As long as syncing works correctly it’s fine but when it goes wrong it can be messy. I’ve known people to lose files because they relied on iDisk sync.

I found this page which has some useful info:
http://homepage.mac.com/rfwilmut/notes/idisksync.html

I think I’ll continue to use my iDisk for backing up documents etc but will use the local copy sync feature to see how reliable it is over time.

So, the “local” iDisk I thought I was accessing this whole time was really just still in the cloud.

I’ve turned local copy on and I’m just waiting for everything to sync up now, then I’m sure Spotlight will work like I thought it would before, and I’ll be ready to make the full time switch.

Spotlight works fine, with one twist: When doing a Command-F, I found my iDisk “hard drive” was not listed for searching. All I got was “This Mac” and my Home directory. I searched “This Mac” and was OK with that since Spotlight is so fast anyway. Still, I wondered if there was a better way…

The trick was to change the Finder preference for new Windows. By default it’s set to your Home directory. I changed it to iDisk, and now a Cmd-F provides “This Mac” and my iDisk volume. (By the way, my iDisk and Home folder have the same name. If yours do too don’t let it confuse you; a quick search will convince you which is being used.)

If you don’t want to change the above default, you can still search the iDisk:

- After a Cmd-F click the iDisk’s icon and start typing a search.
- In the Finder do a Cmd-Shift-I to open the iDisk and then type a search.
- In any Finder window navigate to any iDisk folder and then type in a search.

In all the above, you’ll see “This Mac” with whatever iDIsk folder you navigated to.

Finally, the command-space menu search lists iDisk matches as well.

Yes, that’s correct. If I simply used iDisk as Cloud storage, then it wouldn’t provide the comfort level I get from making the local copy. And, as pointed out, I’d also have the performance lag when reading/writing data.

I’m not sure what advantage (except from saving local disk space, I guess) one would get from NOT creating the local copy. To me it removes one of the primary advantages of MMe’s syncing.

What some people may not realise is that there are two main ways to use iDisk. If you use the standard method which requires a live connection to the net then you may notice delays. If you opt to store a copy of the iDisk on your computer then you’re always working with the local copy so you don’t get the delays. You can set the local copy to sync with the cloud automatically or manually.

MobileMe help pages say this:
“You can use iDisk syncing to create a copy of your iDisk on your computer and make changes to it at any time, even when you’re not connected to the Internet.

Changes you make to the iDisk on your computer are synchronized with your iDisk on MobileMe while you’re connected to the Internet. If you log out, restart, or shut down your computer while your iDisk is syncing, synchronization continues when you log in again.”