6 Disk Raid 1+0

I have an HP Smart Array P400i raid controller, with 6 disks, working in a RAID 1+0. This is what it looks like:

     Mirror Group 0:
        physicaldrive 1I:1:1 (port 1I:box 1:bay 1, SAS, 72 GB, OK)
        physicaldrive 1I:1:2 (port 1I:box 1:bay 2, SAS, 72 GB, OK)
        physicaldrive 1I:1:3 (port 1I:box 1:bay 3, SAS, 72 GB, OK)
     Mirror Group 1:
        physicaldrive 1I:1:4 (port 1I:box 1:bay 4, SAS, 72 GB, OK)
        physicaldrive 2I:1:5 (port 2I:box 1:bay 5, SAS, 72 GB, OK)
        physicaldrive 2I:1:6 (port 2I:box 1:bay 6, SAS, 72 GB, OK)

If my understanding is correct, drives 1 and 2 could fail, and the RAID would still be ok.

This doesn't seem right to me, I was thinking a RAID 1+0, with 6 drives should look like this:

     Mirror Group 0:
        physicaldrive 1I:1:1 (port 1I:box 1:bay 1, SAS, 72 GB, OK)
        physicaldrive 1I:1:2 (port 1I:box 1:bay 2, SAS, 72 GB, OK)
     Mirror Group 1:
        physicaldrive 1I:1:3 (port 1I:box 1:bay 3, SAS, 72 GB, OK)
        physicaldrive 1I:1:4 (port 1I:box 1:bay 4, SAS, 72 GB, OK)
     Mirror Group 2:
        physicaldrive 2I:1:5 (port 2I:box 1:bay 5, SAS, 72 GB, OK)
        physicaldrive 2I:1:6 (port 2I:box 1:bay 6, SAS, 72 GB, OK)

The data would be striped across the 3 mirrored pairs.

Are both configurations possible, or just the first?

You do not have a choice on the drive arrangement/pairs.

In that arrangement HP Smart Array controllers split the disks as such:

physicaldrive 1I:1:1 pairs to physicaldrive 1I:1:4 
physicaldrive 1I:1:2 pairs to physicaldrive 2I:1:5
physicaldrive 1I:1:3 pairs to physicaldrive 2I:1:6 

RAID 1+0 == RAID 1 pairs, striped (RAID 0) together...

You can lose ONE disk from each of the pairings listed above. Or, one drive from each "Mirror Group".

Also: What are the different widely used RAID levels and when should I consider them?