Few questions

[Michael Makuch <linuxraid@makuch.org>]

I realize this is the developers list and though I am a developer I'm 
not a developer
of linux raid, but I can find no other source of answers to these questions:

I've been using linux software raid (5) for a couple of years, having 
recently uped
to the 2.6.23 kernel (FC7, was previously on FC5). I just noticed that
my /proc/mdstat shows

$ cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 etherd/e0.0[0] etherd/e0.2[9](S) etherd/e0.9[8] 
etherd/e0.8[7] etherd/e0.7[6] etherd/e0.6[5] etherd/e0.5[4] 
etherd/e0.4[3] etherd/e0.3[2] etherd/e0.1[1]
      3907091968 blocks level 5, 64k chunk, algorithm 2 [9/9] [UUUUUUUUU]
      [============>........]  resync = 64.5% (315458352/488386496) 
finish=2228.0min speed=1292K/sec
unused devices: <none>

and I have no idea where the raid6 came from. The only thing I've found 
on raid6
is a wikipedia.org page, nothing on 
http://tldp.org/HOWTO/Software-RAID-HOWTO.html

So my questions are:

- Is raid6 documented anywhere? If so, where? I'd like to take advantage 
of it if
it's really there.
- Why does my array (which I configured as raid5) have personalities of
raid6 (I can understand why raid4 would be there)?
- Is this a.o.k for a raid5 array?

Thanks