Re: [Xen-users] Xen and I/O Intensive Loads

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Wed, Aug 26, 2009 at 12:07:55PM -0600, Nick Couchman wrote:
> 
> Doesn't really seem to make a difference which way I do it...I still see 
> pretty intense disk I/O. 
> 
> Here is some sample output from iostat in the domU: 
> 
> Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz 
> avgqu-sz   await  svctm  %util 
> xvdb             12.20     0.00 1217.40   26.20  9197.60   530.80    15.65    
> 29.66   23.47   0.80 100.00 
> 
> Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz 
> avgqu-sz   await  svctm  %util 
> xvdb             18.40     0.00 1121.20   19.60  8737.60   691.50    16.53    
> 32.97   29.13   0.88 100.00 
> 
> Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz 
> avgqu-sz   await  svctm  %util 
> xvdb             27.80     0.00 1241.40   29.20  8158.40   377.90    13.44    
> 42.59   33.73   0.79 100.00 
> 
> Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz 
> avgqu-sz   await  svctm  %util 
> xvdb             31.60     0.00 1256.60   35.00  9426.40   424.00    15.25    
> 42.06   32.44   0.77 100.00 
> 
> Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz 
> avgqu-sz   await  svctm  %util 
> xvdb             57.68     0.00 1250.50   17.76  8588.42   352.99    14.10    
> 51.36   40.60   0.79  99.80 
> 
> the avgqu-sz is anywhere from 11 to 75, and the await is anywhere from 20 to 
> 50.  %util is always around 100. 
> 

Well.. it seems your SAN LUN is the problem. Have you checked the load
from the FC Storage array?

Or then the problem is in your FC HBA. Have you verified the FC link is at full 
speed? 

Are the FC switches OK?

Do you have up-to-date HBA driver in dom0? Are the HBA/Switch/Storage
firmwares up-to-date?

-- Pasi


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