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Re: [Xen-users] Sharing Disk Access Time

To: Russ Purinton <rpurinton@xxxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-users] Sharing Disk Access Time
From: Teck Choon Giam <giamteckchoon@xxxxxxxxx>
Date: Wed, 15 Dec 2010 03:10:00 +0800
Cc: xen-users@xxxxxxxxxxxxxxxxxxx, Roberto Bifulco <roberto.bifulco2@xxxxxxxx>
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On Wed, Dec 15, 2010 at 2:16 AM, Russ Purinton <rpurinton@xxxxxxxxxxxxxxxxxxxxxxx> wrote:

It appears Roberto has gone far beyond any testing I’ve ever done, but I’ve always been concerned about disk access.  I have a Xen server with RAID 1 SATA drives internal using img files. The host is CentOS 5.5.


I notice that whenever I build a new VM and it gets to where it is allocating the img file, the entire time it is allocating the space for it, all my other virtual machines effectly stop doing anything.


One DomU is a windows terminal server.  While logged into it, I started the Image allocation then tried to open MS Outlook on the terminal server.  Everything hung until the disk allocation was completed, then Outlook finally opened 30 minutes later.


Is there a way to do ‘fair-sharing’ of disk IO time so that a single DomU cannot hog all the physical IO capacity?

Just curious... ... are you using AHCI mode?

Command to check:
# cat /etc/modprobe.conf | grep scsi_hostadapter


Kindest regards,
Giam Teck Choon
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