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Re: [Xen-users] Speed of Xen Network Bridge Interface (10/100/1000?)

  • To: "Xen Users" <xen-users@xxxxxxxxxxxxxxxxxxx>
  • From: "Javier Guerra" <javier@xxxxxxxxxxx>
  • Date: Tue, 27 Nov 2007 12:27:25 -0500
  • Delivery-date: Tue, 27 Nov 2007 09:28:10 -0800
  • List-id: Xen user discussion <xen-users.lists.xensource.com>

On 11/27/07, Emre Erenoglu <erenoglu@xxxxxxxxx> wrote:
> Hi,
> I would like to learn the speed of the network bridge interfaces created by
> XEN.
> More specifically, on xenbr0, given that the traffic only occurs between my
> Dom0 host and PV DomU guest, am I limited to 10 Mbps, 100 Mbps or 1000 Mbps?
> Does it depend on something such as ethernet card capability (even though
> the packets don't go out of the card and stay inside Dom0)?
> I plan to use iScsi or Ata-over-Ethernet, that's why I'm asking this
> question,

AFAIK, there's no hard speed limit.  on HVM guests, the eth card
appears as a 10Mbit model, but usually performs much faster than that.

OTOH, any block device protocol with the initiators on DomU is
certainly doable, but you get huge overheads.  be sure to dedicate at
least one physical CPU core to Dom0, so that you don't get two
context-switchs (with associated blocking) for each packet.

IMHO, you always want to use highest-level, biggest-block abstractions
on DomU's, with any low-level, small-block implementations terminated
at Dom0.  in your case, the iSCSI initiator or AoE module would be on
Dom0, and DomU's would see only block devices, without any special

why would you want to run AoE/iSCSI over the emulated LAN? is it to
make it easier to live-resize the block devices?  there should be a
better way...


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