drush update fails with "failed to backup project directory ... to ..."

No idea, really, but this is a slightly better title.

Somehow, drush is getting a wrong path to backup - it's apparently trying to backup /var/www/drupal instead of the directory of the module that's about to be udpated.

Please re-run it with the -v flag for more verbose output and post here again if the problem persists.

Check out this and let me know if it helps - #305489: drush and multi-site and update/backup - It's for the drupal 6 version but probably very similar

I am getting this problem too, with drush 6.x-1.1, but only when it tries to update themes. Updating modules works fine. I tried miimooo's patch, but it did not help.

Ok, I did this and what I get is the backup directory with the dreaded "99 99" (nobody nobody) owner and group with 775 permissions. Then, i can't even delete that folder (not rename, not copy anything inside).

Same issue here. The verbose output is below:

$ drush -v --cvsmethod=update pm update gmap
Update information last refreshed: Thu, 10/09/2008 - 9:03am

Update status information on all installed and enabled Drupal modules:
  Name       	Installed version	Recommended version	Status          
  ----       	-----------------	-------------------	------
  GMap Module	6.x-1.0-beta5    	6.x-1.0-rc1        	Update available

Updates are available for the following projects:
GMap Module [gmap]

Note: Updated modules can potentially break your site. It's not recommended to update production sites without prior testing.
Note: If you have made any modifications to any file that belongs to one of these projects, you will have to migrate those modifications after updating.
Do you really want to continue? (y/n): y
Starting to update GMap Module ...
Calling mkdir(/Users/foo/Sites/site9/fof/trunk/drupal/backup, 511)
Calling mkdir(/Users/foo/Sites/site9/fof/trunk/drupal/backup/modules, 511)
Calling mkdir(/Users/foo/Sites/site9/fof/trunk/drupal/backup/modules/20081009091343, 511)
Calling rename(/Users/foo/Sites/site9/fof/trunk/drupal/, /Users/foo/Sites/site9/fof/trunk/drupal/backup/modules/20081009091343/gmap)
drush: Failed to backup project directory /Users/foo/Sites/site9/fof/trunk/drupal/ to /Users/foo/Sites/site9/fof/trunk/drupal/backup/modules/20081009091343/gmap

I am having this issue on 6.x-1.x-dev. Any help in solving would be much appreciated.

jdblank: Try the patch in #324803: cvsmethod=update fails because backup removes the original project
It's not actually a direct fix for this issue (they seem like different problems IMHO), but it will function as a workaround since it skips backups when CVS updates are happening.

OK i will try this although we are using wget method not cvs

Ah sorry, my mistake. If using wget I doubt that patch will be of much help to you.

BTW I'm removing the "needs more info" status since that was a request for -v output which we have now...