@Albert ...
After completing successfully, Moodle should 'clean up' the temp directory it created and the only item one should see is a 0 byte file with the autogenerated directory name .log.
Any .log file that is larger than 0 bytes has some clues in it.
No directory like qwer453ljqerjsdflf should exist.
What do those files look like?
In http://yoursite/admin/settings.php?section=experimentalsettings
do you have
Enable new backup format turned on?
"If enabled, future backups will be created in a new compression format
for .mbz files (internally stored as a .tar.gz file). This removes the
4GB backup size restriction and may improve performance. Restore
supports both formats and the difference should be transparent to users."
Last I heard, Windows servers don't come with supports for .tar.gz.
And, there have been issues on the Windows platform where temp files/folders couldn't be 'cleaned up' - ie, erased from the system.
I too have watched, in real time, the entire process. On systems that have PHP 5.3.x APC opcache there seems to be issues with the *copy* method used by Moodle code to 'move' the built .mbz file to it's final destination. That last step is where one sees the progress bar get to like 96.x% and appears to hang (ie, there is a long wait). If it is successful doing that, then the routine can and does remove the temp directory and the only thing remaining is a 0 byte log file.
I, too, have had issues with autobackups. Have set them to manual now. Set send to designated directory outside of moodle's filedir/filesystem, removed the logs in the backup ... basically attempting to run the autobackup as a method of re-setting each course.
Have ID'd the courses that are large using 'course sizes' addon.
Use that info to gather info for using backup.php (a cli file found in version 2.7 of Moodle - I've downloaded the code and copied that file into the admin/cli/ directory of a 2.6.highest.
That backs up individual courses. Use it to troubleshoot the large course issues.
That script, as well as autobackups, reads settings from the form for backups. While I know a full course backup is desired, will take what I can get right now. Something is better than nothing! :|
'spirit of sharing, Ken