Firstly, I have read these:
(1) http://www.gaiagps.com/news/article/iOS5%20Breaks%20Data%20Storage%20and%20Crushes%20My%20Soul
(2) http://iphoneincubator.com/blog/data-management/local-file-storage-in-ios-5
(I can not submit more than two hyperlinks because I'm a noob.)
and all the related developer forum threads in apple.com.
Problem: with the new iOS5, we need to save files to /Caches folder, and save only user generated files to the /Documents folder. And caches folder may be deleted unexpectedly even when our app is not running, on app updates or system restores. The deletion at an unexpected time is the one that worries us.
The reason I am still opening a question about the same issue is to ask;
1. If I am missing anything. As if there's an update on this issue and I am the only one that didn't hear it. The guy from the first link (gaiagps) is complaining about having their app rejected and so, but his following blog post is telling their app data is now safe from deletion.
2. Is it okay to save my data to /Documents (even if they're big -to ruin the iCloud user experience-), using the new component UIDocument and syncing it with iCloud storage?
I would like to develop the app correctly to get accepted by the app review the first time I submit the app (if possible), to avoid any latencies. So what I am asking is, where to save the data in iPad so it won't get deleted?
Apple has fixed this issue in iOS 5.01 beta.
See my blog post here:
There are a few key points to remember here...
The documents directory is for files which cannot be easily recreated or downloaded. For instance, if an app downloads some common files to the users device, this should not go in the documents directory as it is not really specific to the user and can be easily re-downloaded.
Items which are created specific to the user and which may be difficult to recreate should be stored in the documents folder, for instance a PDF which is created via user input or editing.
Any files in the documents directory will be included in back-ups, whether that be to iTunes or to iCloud so storing overly large files in the documents directory is likely to upset your users.
You should only save user generated documents in the Documents folder. App generated data generally goes into a subdirectory of the Library directory or tmp for short lived data.
If you need to make sure your app generated data is not automatically purged you can use the "Application Support" directory.
A have provided a more detailed answer to a similar question here.
I had the same issue with my App and Apple rejected my app as I was storing my data into /Document directory;
Here are my findings which I documented in a blog post; http://aasims.wordpress.com/2012/02/02/storage-issue-with-ios-5-and-icloud/
来源：https://stackoverflow.com/questions/7977574/ios5-data-storage-issue-where-to-save-files