Steve Snyder wrote:
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
Raid1 is supposed to let the disks read independently but I'm not sure
if it works that way when there is only a single read happening. I'd
expect a bigger difference when reading many small files simultaneously
and the drive with the head nearest to the right place is used for
each access.
--
Les Mikesell
lesmikesell@xxxxxxxxx
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