On 04/05/2011 01:07, Liam Kurmos wrote:

Hi,

I've been testing mdadm (great piece of software btw) however all my
test show that reading from raid1 is only the same speed as reading
from a single drive.

Is this a known issue? or is there something seriously wrong with my
system? i have tried v2.8.1 and v.3.2.1 without difference and several
benchmarking methods.

This is a FAQ. Yes, this is known. No, it's not an issue, it's by design 
- pretty much any RAID 1 implementation will be the same because of the 
nature of spinning discs. md RAID 1 will serve multiple simultaneous 
reads from the different mirrors, giving a higher total throughput, but 
a single-threaded read will read from only one. If you want RAID 0 
sequential speed at the same time as RAID 1 mirroring, look at md RAID 
10, and in particular RAID 10,f2; please see the excellent documentation 
and wiki for more details.

Cheers,

John.