[CentOS] md raid1 - no speed improvement

On Sunday 23 March 2008 7:11:41 am Kieran Clancy wrote:
[snip]
> So the total cached read bandwidth seems limited to about 2250 MB/s,
> which is slightly higher than the cache read bandwidth for /dev/md2,
> but I'm not too worried about that. More concerning is that I am
> still getting ~80MB/s from each disk simultaneously on the buffered
> reads. Given this I would expect /dev/md2 to give buffered read
> speeds of at least 120MB/s (if not 150MB/s).

The value of RAID 1 isn't speed. it's fault tolerance.  I would expect 
what you're seeing, a slight performance *loss* (relative to a single 
disk) due to the additional overhead of the RAID management.

http://www.linuxhomenetworking.com/wiki/index.php/Quick_HOWTO_:_Ch26_:_Linux_Software_RAID#RAID_1