For backup purposes we have Cifs file Server running that contains encrypted containers for backing up the more sensitive data. The container is mounted with cryptsetup and loop as a local filesystem and the rsync is used for backups.

Because the Cifs server is not the fastest machine ever built, running the rsync process results in an iowait on the servers running the backup which in turn drives Nagios into an email frenzy. The question is, how do reduce the iowait on the server? Configuring Nagios to not report seems more like a workaround then a solution. Stretching the backups over different time intervals is already done with little effect and spending money is also not an option because apparently, we are talking about a "non-critical system".