pkgacct / gzip killing server load

Well the first thing I would do is exclude "backup-*.tar.gz" files from the backup system as one of the most common mistakes made is users making their own backup archives and leaving them on their account daily so what happens is that you get a ping pong backup effect where you end up generating a backup of a backup of a backup and so forth and end up with really enough backups that are slow to build and utterly pointless.

The second thing to take a hard look at is the web site access logs and statistics cache for the site as these can build quite large especially if sites have high traffic or log rolling is not enabled. These can also slow down your backup process and increase the loads as well.

Also, you may want to check for symlinks and in particular pay attention to any that might result in a possible looping situation such as for example symlinking to ../public_html from within public_html, etc.

Code:

# find /home/*/public_html -type l

If client's (or your own sites) are using applications that "cache" data which is a fairly common technique for many applications, you may want to clear the cache that they generate periodically.

You also may want to play around with "incremental" or regular "normal" archival backups depending on your situation each has it's own set of advantages and disadvantages.