Re: RAID-5 streaming read performance

[Dan Christensen <jdc@uwo.ca>]

Here's a question for people running software raid-5:  do you get
significantly better read speed from a raid-5 device than from it's
component partitions/hard drives, using the simple dd test I did?
Knowing this will help determine whether something is funny with my
set-up and/or hardware, or if just had unrealistic expectations about
software raid performance.

Feel free to reply directly to me if you don't want to clutter the
list.  My dumb script is below.

Thanks,

Dan

#!/bin/sh

dd if=/dev/sda8 of=/dev/null bs=1M count=900 > /dev/null 2>&1
for f in sda7 sdb5 sdc5 sdd5 ; do 
  echo $f; 
  dd if=/dev/$f of=/dev/null bs=1M count=300 2>&1 | grep bytes/sec
  echo; 
done

dd if=/dev/sda8 of=/dev/null bs=1M count=900 > /dev/null 2>&1
for f in md2 ; do 
  echo $f; 
  dd if=/dev/$f of=/dev/null bs=1M count=300 2>&1 | grep bytes/sec
  echo; 
done