[linux-lvm] LVM iostat readings

[Lyn Rees <Rees cardiff ac uk>]

Anyone?

__________________

Hi,

I've had a good look around for answers
but found nothing useful.

I've collected data using iostat from
a production server. I've got 3 disks stitched together as a linear LVM,
250GB+500GB+500GB, with data on only the first 2 disks at the moment.

Under load, the PV's get busy showing
high utilisation (%util) and quite high queue depths (avgqu-sz). the LV
however hits 100% utilisation and the queue depth gets huge! Performance
becomes poor at these times, suggesting the values are representative of
what is actually happening.

Can someone help me understand what's
going on here please? Could LVM be causing a bottleneck, or is a physical
bottleneck causing this?

Thanks,
Lyn Rees.
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Mr Lyn Rees
Senior Engineer, UIG
Information Services Computing Centre
Cardiff University, 40-41 Park Place,
Cardiff. CF10 3BB.
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Contact numbers:
 (029) 2087 9188 (direct)
 (029) 2087 4875 (reception)
 (029) 2087 4285 (fax)
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Email: rees cardiff ac uk
Web: www.cardiff.ac.uk