I am looking at using unRAID 4.5 as a system to regularly back up my home WHS server. I was wondering if I did not install/enable the parity drive whether that would make sense as this would be a back up of another device rather than the original files. It seems as if using the parity drive will slow down transfers, as well as using up hard drive space...

You could do that, but why? It's only 1 disk out of 'N', unlike WHS which uses up half of N for protected storage. I'm assuming you wouldn't be doing a naive exact copy backup and you'd like to have the data available for some duration of time.

 

You could easily run into the following case:

 

1) You realize you accidentally deleted some files from WHS, you'd like to restore.

2) The drive containing the files in the NON-PROTECTED unRAID died.

3) You scream loudly as you realize you lost the files forever.

 

For the cheap cost of a singular parity drive, you can avoid this situation.

 

Even in the case of incrementally backing up PC_A to WHS_B that's incrementally backed up to unRAID_C, I'd still run with a parity drive. My time, sanity, and peace of mind is worth far more than that of a singular parity drive ($100/$170 for 2TB 5400/7200 rpm drive).

thanks for the feedback - the cost is not that much of an issue I guess. 60 bucks for unRaid and then $90 for a 1TB - the rest of my system is using an old box (P4 3.0 GB with 1 GB of RAM) and a gigabit PCI network card. I suppose the speed is not too much of a problem either as once the first backup is done, then further copies would not be so big...