Disk IO issues

[Mike McGrath]

On Thu, 1 Jan 2009, James Antill wrote:

> On Wed, 2008-12-31 at 14:42 -0600, Mike McGrath wrote:
> > Lets pool some knowledge together because at this point, I'm missing
> > something.
> >
> > I've been doing all measurements with sar as bonnie, etc, causes builds to
> > timeout.
> >
> > Problem: We're seeing slower then normal disk IO.  At least I think we
> > are.  This is a PERC5/E and MD1000 array.
> >
> > When I try to do a normal copy "cp -adv /mnt/koji/packages /tmp/" I get
> > around 4-6MBytes/s
>
>  This _might_ not be "IO" in a normal sense, -a to cp means:
>
>  file data + file inode + ACLs + selinux + xattrs [+ file capabilities]
>
> ...esp. given that you aren't getting large IOWait times, you might want
> to strace -T the cp and do some perl/whatever on the result to see what
> is eating up the time.

Even with non cp type things (like a bacula backup) it just doesn't seem
as fast as I would expect it to be.  I've never actually done trending at
this level / scale on a filesystem / drive before.  So I really don't have
a good baseline except that it just seems slow to me.

Other then the much faster direct block access and the large file reads, I
don't have much else to go on that makes me think its slow.

>  This is a straight 5.2, yeh?
>

Correct.

	-Mike