resiliency for RAID 10 grows in larger arrays
RAID 10 and RAID 6 both require a minimum of 4 disks.
When RAID 10 loses a disk you still have your RAID 0 stripe spanning your two (or more) mirrors albeit one mirror has a failed drive. The next drive you lose will cause total failure if the drive that fails is on the mirror that already has a failed drive. If it is on the other mirror no effect.
For data protection this is obviously worse than RAID 6 where any two drives can fail and you have not lost data.
A RAID 10 array with say 12 disks stores the equivalent of an 8 disk RAID 6 array. Loss of two disks can fail the whole array but the odds are now reduced to a 9% chance (1/11) the next failure will be on the one drive that will cause total failure.
Potentially this array could lose six disks with no data loss.
However, no matter the number of disks in the array two failures in the same mirror still result in total failure(unless you mirror to multiple disks which really puts cost up).
RAID 10 also has the advantage of minimal impact on disk speed during the rebuild.
RAID 6 gets less resilient as the array grows. This can be combated by keeping arrays smaller and using RAID 60, or in the extreme there is the suggestion above for use of RAID 16. If you need 100% uptime RAID 16 could be an option. The rebuild time is minimised by the mirrors, and the susceptibility to total failure is minimised by the overlying RAID6
When considering protection against failure during rebuild RAID 10 has the advantage that you are only rebuilding a single drive mirror.
