On Tue, Nov 01, 2011 at 04:13:26PM -0400, Miles Fidelman wrote:

David Brown wrote:

quoted

No, md RAID10 does /not/ offer more redundancy than RAID1.  You are 
right that md RAID10 offers more than RAID1 (or traditional RAID0 over 
RAID1 sets) - but it is a convenience and performance benefit, not a 
redundancy benefit.  In particular, it lets you build RAID10 from any 
number of disks, not just two.  And it lets you stripe over all disks, 
improving performance for some loads (though not /all/ loads - if you 
have lots of concurrent small reads, you may be faster using plain 
RAID1).

In fact raid10 mas a bit less redundancy than raid1+0.
It is as far as I know built as raid0+1 with a disk layout
where you can only loose eg 1 out of 4 disks, while raid1+0
in some cases can lose 2 disks out of 4.

Also for lots of concurrent small reads raid10 can in some cases be somewhat
faster than raid1, and AFAIK never slower than raid1. 

Best regards
keld