On Mon Jan 31, 2011 at 01:32:06PM -0200, Roberto Spadim wrote:

rewriting..
using raid10 or raid01 you will have problems if you lose 2 drives too...
if you lose two raid 1 devices you loose raid 1...
see:

disks=4
RAID 1+0
raid1= 1-2(A)  ; 3-4(B); 5-6(C)
raid0= A-B-C
if you lose (A,B or C) your raid0 stop

RAID 0+1
raid0= 1-2-3(A)  ; 4-5-6(B)
raid1= A-B
if you lose (1,4 OR 1,5 OR 1,6 OR 2,4 OR 2,5 OR 2,6 OR 3,4 OR 4,5 OR
4,6) your raid0 stop

using raid1+0 or raid0+1 you can't lose two disks...

Yes you can - it just depends which disks. With the 6-disk case you can
lose a maximum of 3 drives, though only a single drive failure will
definitely not cause total array failure.  For RAID1+0 your 2-drive
failure cases are only 1,2 OR 3,4 OR 5,6 - any other pairing will not
break the overall array.  For RAID0+1 there's 9 failure cases as you
point out (except the last two should be 3,5 and 3,6).

Cheers,
    Robin