WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

RE: [Xen-devel] Re: Questions on Copy-on-Write

To: "Christian Limpach" <chris@xxxxxx>
Subject: RE: [Xen-devel] Re: Questions on Copy-on-Write
From: "Williamson, Mark A" <mark.a.williamson@xxxxxxxxx>
Date: Mon, 2 Feb 2004 14:36:32 -0000
Cc: "Devel Xen" <xen-devel@xxxxxxxxxxxxxxxxxxxxx>
Delivery-date: Tue, 03 Feb 2004 23:32:25 +0000
Envelope-to: steven.hand@xxxxxxxxxxxx
List-archive: <http://sourceforge.net/mailarchive/forum.php?forum=xen-devel>
List-help: <mailto:xen-devel-request@lists.sourceforge.net?subject=help>
List-id: List for Xen developers <xen-devel.lists.sourceforge.net>
List-post: <mailto:xen-devel@lists.sourceforge.net>
List-subscribe: <https://lists.sourceforge.net/lists/listinfo/xen-devel>, <mailto:xen-devel-request@lists.sourceforge.net?subject=subscribe>
List-unsubscribe: <https://lists.sourceforge.net/lists/listinfo/xen-devel>, <mailto:xen-devel-request@lists.sourceforge.net?subject=unsubscribe>
Sender: xen-devel-admin@xxxxxxxxxxxxxxxxxxxxx
Thread-index: AcPpk3QGpMqcosnxRTOkP/wq56OaRAAA/nkA
Thread-topic: [Xen-devel] Re: Questions on Copy-on-Write
> Doesn't this sit at the wrong level?  This would make all 
> disk accesses on
> these devices go through Domain0?

That's not quite right: virtual block devices are an abstraction
provided by Xen and domains that use them talk to Xen directly, without
going through Dom0.  VBDs are a way of securely sharing portions of the
physical disk space in the system between domains - Dom0 creates VBDs to
tell Xen what domains can access what parts of the disk.  Those domains
then talk to Xen directly to access those areas.

A domain could be given read only access to the VBD with a "standard
image" for all domains on it and read-write access to another VBD for
it's own personal use.  Using Bin's CoW driver, the domain can then
store all its updates to the standard image in the read-write VBD.  The
domain then talks directly to Xen in order to access these VBDs, same as
usual.

HTH,

Mark


-------------------------------------------------------
The SF.Net email is sponsored by EclipseCon 2004
Premiere Conference on Open Tools Development and Integration
See the breadth of Eclipse activity. February 3-5 in Anaheim, CA.
http://www.eclipsecon.org/osdn
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.sourceforge.net/lists/listinfo/xen-devel

<Prev in Thread] Current Thread [Next in Thread>
  • RE: [Xen-devel] Re: Questions on Copy-on-Write, Williamson, Mark A <=