4 x 2TB drives, safe to use RAID-5? What is failure rate

I had a WHS a while ago, but have recently migrated my box to a Linux setup with the following:

• Fedora 14 running headless / non-graphical (have VNCserver installed for remote desktop if needed)
• Amahi using Greyhole - mainly for the drive-pooling functionality.

Hardware-wise am running a box with:

• 5x1TB [insert brand] Green disks (low power consumption)
• 2GB RAM
• 1.6Ghz Atom

Using combination of cron and rsync this then creates an external backup of critical data to a USB-connected 2TB drive everyday (in addition to the Greyhole duplication).

With DDWRT on my router and a free account with DynDNS I'm able to access my server from anywhere.

From personal experience, VMs aren't really that useful in a home environment - I personally want a low-power, low-cost box and running multiple VMs on that will just cripple performance. Not sure what all your uses are going to be, but found the setup above ample for file-storage / sharing, media streaming (including 1080p) and FTP server.

Per the Wiki I notice that Amahi also has the following (although haven't used it myself):

Remote VPN access to your Amahi HDA comes pre-configured out of the box

Just to note that the AMD RAID solution in the SB950 is not a "hardware RAID" solution.

The message about the array not being initialised would indicate that the array is initialized in background, there is nothing intrinsically wrong with this, but performance should improve when initialisation has completed.