On Tue Nov 01, 2011 at 04:13:26 -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).

wasn't suggesting that it does - just that it does things differently 
than normal raid 1+0 - for example, by doing mirroring and striping as a 
unitary operation, it works across odd number of drives - it also (I 
think) allows for more than 2 copies of a block (not completely clear 
how many copies of a block would be made if you specified a 16 drive 
array) - sort of what I'm wondering here

By default it'll make 2 copies, regardless how many devices are in the
array. You can specify how many copies you want though, so -n3 will give
you a near configuration with 3 copies, -n4 for four copies, etc.

Cheers,
    Robin
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