Speed up backup to NAS

[cpradio]

Currently I have two NASes, one mirrors the other via a nightly backup. However, that backup is taking 2 days to complete, which doesn't quite make me happy. The data on the primary nas doesn't change enough to warrant that long of a process.

Is there a way I can set it up to run quicker?
Right now the settings are:
Schedule: Every Day
Time: 00:00
Operation Mode: Overwrite Backup (Differential Backup)

Options Checked:
Create Backup Log File
Ignore backup failure and continue on schedule
Exclude Trash
Complete Backup

Prior to my hard drive failures, I was certain this process only took a few hours. Now it takes 2 days!
The initial backup took 3 days, and the data that is different daily should just be a few gigs (under 5).

So why is the backup taking 2 days to run after the initial backup?

[asbr]

I think it is because you have selected 'complete backup'.

I too find the options confusing and wish they were better described. I am currently running both 'Differential backup' and 'Append backup', when what I want is one backup that stores the latest version of all files and retains files that have been deleted. However the Differential backup seems to do all that is necessary. All the 'Append' backup seems to do is add the backup log file created by the 'Differential' backup that has just run.

'Normal' backup seems to make a copy of all files into a folder which is given the date/time as a name. 'Complete backup' seems to make a copy of all files every time it is run, overwriting ones that have already been copied on previous backups with updated versions. It creates a folder called '_backups'' the first time it is run. Append' and 'Differential' copy files into the '_backups' folder that a 'Complete' backup has created, overwriting ones that have been changed.

But I'm not pretending I understand all this. If someone can put it more simply I would be grateful