CERC RAID5 performance lower than everyone else

[John Hodrien]

On Mon, 21 Jul 2008, Jim Nelson wrote:

> Helped on our machine too - that's a rather useful bit of information now in my
> rc.local :)
>
> We'll be retiring our box in a few months, but that should take a day or two off
> the data transfer time...

Just out of interest I thought I'd try a test to see what difference it made
on our CERC.  I'm not drawing any conclusions from the results ;)

# blockdev --setra 0 /dev/sda
hdparm -t /dev/sda

setra   MBytes/sec (read)
0        5.36
1        5.58
2        5.61
4        7.90
8       12.64
16      20.96
32      33.60
64      40.90
128     57.57
256     57.75   This is the default as set on the box with CentOS 5
512     57.90
1024    57.82
2048    57.46
4096    57.86
8192    57.75
16384   56.59
32768   55.54
65536   46.07
131072  23.98
262144  15.06

jh

-- 
"A good scientist is a person with original ideas.  A good engineer is a
  person who makes a design that works with as few original ideas as possible.
  There are no prima donnas in engineering."          -- Freeman Dyson