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OpenVZ IO Isolation ? [message #42557]

Thu, 28 April 2011 14:22

andre
Messages: 36
Registered: January 2008

Member

Hello,

We have been working with OpenVZ for some years on some servers and have found a problematic behavior with one of our customers.

There are just 2 VE's on this hardware (let's call them VE1 and VE2). Each one with 25% of the resources (to give room for more 2 VEs that would be activated later). It is a Core2Quad with 8GB RAM and RAID1 SATA.

The problem:

VE1 is able to slow down the whole server, making IOWAIT for all VEs really high. To make sure it was not hardware related, we moved the VEs to another hardware (with latest stable kernel: 2.6.18-238.5.1.el5.028stab085.2) and got the same behavior.

Each VE has CPULIMIT=90% and CPUS=1

Reading "IOACCT", read/write/nice/etc information seems pretty "normal" but DIRTY BYTES is high.. So I thought: Could OpenVZ IO scheduler not be counting this ?

I am not a kernel expert (nor have basic kernel coding knowledge), just trying to understand what could cause this and if there are any solutions. At this moment we are keeping VE1 alone at a hardware so it won't impact other customers.

IOWAIT shows VE1's mysqld as the responsible. One VE's process being able to make the whole node near 100% IOWAIT is worrying Sad

Thanks.

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[Message index]

		OpenVZ IO Isolation ? By: andre on Thu, 28 April 2011 14:22
		Re: OpenVZ IO Isolation ? By: seanfulton on Sun, 01 May 2011 18:10
		Re: OpenVZ IO Isolation ? By: seanfulton on Tue, 03 May 2011 20:40
		Re: OpenVZ IO Isolation ? By: swindmill on Thu, 05 May 2011 17:07
		Re: OpenVZ IO Isolation ? By: seanfulton on Thu, 05 May 2011 18:28
		Re: OpenVZ IO Isolation ? By: swindmill on Thu, 05 May 2011 18:37
		Re: OpenVZ IO Isolation ? By: seanfulton on Thu, 05 May 2011 18:46
		Re: OpenVZ IO Isolation ? By: andre on Tue, 30 August 2011 00:58
		Re: OpenVZ IO Isolation ? By: seanfulton on Tue, 30 August 2011 15:26
		Re: OpenVZ IO Isolation ? By: andre on Wed, 31 August 2011 20:27
		Re: OpenVZ IO Isolation ? By: mustardman on Fri, 02 September 2011 17:04
		Re: OpenVZ IO Isolation ? By: seanfulton on Fri, 02 September 2011 18:06
		Re: OpenVZ IO Isolation ? By: seanfulton on Fri, 02 September 2011 18:11
		Re: OpenVZ IO Isolation ? By: mustardman on Fri, 02 September 2011 20:37
		Re: OpenVZ IO Isolation ? By: andre on Tue, 06 September 2011 02:32
		Re: OpenVZ IO Isolation ? By: raver119 on Tue, 13 September 2011 00:10

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