I am setting up some new servers (Dell PowerEdge T710) that have 4 SAS drives connected to the internal PERC controller.

I am setting up an external storage bay with RAID 5 and some hot spares to be used for the user data.

For the 4 internal SAS drives, I was planning on setting it up as a RAID 1 mirror set, with 2 hot spares for the OES 2 SP1 install.

I have been told I should go with RAID 5 plus 1 hot spare.

Any opinions? I figured RAID 1 would have less overhead for performance. Does it really matter? I prefer RAID 1 for OS.