NeilBrown wrote:

On Tue, 1 Nov 2011 23:15:39 +0100 keld@keldix.com wrote:

quoted

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

quoted

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.

With md/raid10 you can in some case lose 2 out of 4 disks and survive, just
like raid1+0.

it occurs to me that it's a real bummer that all the md documentation, 
that was on raid.wiki.kernel.org, has been inaccessible since the 
kernel.org hack a couple of months ago -- anybody know if that's going 
to be back soon, or if that documentation lives somewhere else as well?




-- 
In theory, there is no difference between theory and practice.
In<fnord>  practice, there is.   .... Yogi Berra