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Re: [Xen-users] Best practice for presenting disk to (HVM) RHEL DomUs?

To: Robert Sturrock <rns@xxxxxxxxxxxxxx>
Subject: Re: [Xen-users] Best practice for presenting disk to (HVM) RHEL DomUs?
From: Christian Horn <chorn@xxxxxxxxxxxx>
Date: Tue, 25 Sep 2007 19:14:28 +0200
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On Mon, Sep 24, 2007 at 05:43:26PM +1000, Robert Sturrock wrote:
> [HVM] 
> I have an existing RHEL4 DomU here that I'd like to present some extra
> to.  An extra pair or 146G SCSI drives have been made available in the
> Dom0, and I'm trying to work out how best to present them entirely to
> a single DomU.
> Ultimately I want the disks to be setup as a Software mirror and
> mkfs'd into a single ~140GB partition.  Can people recommend the best
> way to do this to yield good I/O performance?
> I'm not sure whether I should make the software mirror on the Dom0 and
> then present /dev/mdX to the DomU (assuming this is possible).  Or
> should I just present the raw disks straight to the DomU and let the
> DomU handle the mirroring?

Presenting the two disks to the HVM-domU and making the raid1 in the
domU will to my understanding double the i/o that the qemu-device-
emulation hast to handle.
Placing the raid1-operation in the dom0 will do it there and the data
has to travel only once into the domU.

If the domU was paravirtualized i wouldnt be sure if the dom0 can
handle the raid1 faster than the domU.


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