Re: XFS IO multiplication problem on centos/rhel 6 using hp p420i raid controllers

Dennis Kaarsemaker
2013-03-07T13:52:34Z

On Thu, 2013-03-07 at 07:44 -0600, Stan Hoeppner wrote:
> On 3/7/2013 7:33 AM, Dennis Kaarsemaker wrote:
>
> > The "ten times as many bytes" is constant, so it is constantly writing
> > ten times as much data.
>
> Where in the IO stack are you counting the bytes? Are 10x as many bytes
> actually hitting the AGs? I.e. are you consuming 10x more (real--not
> counting preallocation) space in the filesystem? Or are you simply
> seeing larger IOs in flight per unit time, but the same total amount of
> IO bytes?

I'm counting them with vmstat, iostat and collectl as can be seen in the
various outputs I've sent. I hope that answers your question as I have
no idea how to see what's hitting the AG's.

I am not using ten times as much space, as that wouldn't fit on the
volume.