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RE: [Xen-users] Sharing Disk Access Time

To: "Teck Choon Giam" <giamteckchoon@xxxxxxxxx>
Subject: RE: [Xen-users] Sharing Disk Access Time
From: "Russ Purinton" <rpurinton@xxxxxxxxxxxxxxxxxxxxxxx>
Date: Wed, 15 Dec 2010 11:26:32 -0500
Cc: xen-users@xxxxxxxxxxxxxxxxxxx, Roberto Bifulco <roberto.bifulco2@xxxxxxxx>
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Thread-topic: [Xen-users] Sharing Disk Access Time

I’m guessing Yes based on this:


[root@xen1 ~]# cat /etc/modprobe.conf | grep scsi_hostadapter

alias scsi_hostadapter ahci

alias scsi_hostadapter1 usb-storage


Is this good for me or bad?


Thank You


From: Teck Choon Giam [mailto:giamteckchoon@xxxxxxxxx]
Sent: Tuesday, December 14, 2010 2:10 PM
To: Russ Purinton
Cc: Roberto Bifulco; xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Sharing Disk Access Time



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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