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RE: [Xen-users] XEN - networking and performance

  • To: "'xen-users'" <xen-users@xxxxxxxxxxxxxxxxxxx>
  • From: <admin@xxxxxxxxxxx>
  • Date: Thu, 6 Oct 2011 14:12:30 -0500
  • Delivery-date: Thu, 06 Oct 2011 12:12:50 -0700
  • Importance: Normal
  • List-id: Xen user discussion <xen-users.lists.xensource.com>
  • Thread-index: AcyET7DGAK9KKKCwT02x+8B6uYs3sgAC3gmw

One thing I would suggest is using RAD10 instead of RAID5.  RAID5 is frequently a performance bottleneck. 


-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of fpt stl
Sent: Thursday, October 06, 2011 12:44 PM
To: xen-users
Subject: [Xen-users] XEN - networking and performance


Greetings all,


I would like some advice from people how are/were using  Xen 3.4.2 - it should be a rather stable release.

Dom0 is CentOS 5.5 64bit with Xen 3.4.2 installed with the default settings (minus cpu pinning to Dom0 and memory setup for 2GB).

There are 2 built-in nics (Broadcom) and an add-on network card (Intel) with another 4 nics.

Currently only one NIC is used for all network access, and as far as networking, the default setings are used - xend-config.sxp:

(network-script network-bridge)

(vif-script vif-bridge)


The questions are:


How can I improve the network performance (now all the VM are sharing one bridge):


a. creating multiple bridges and assigning a VM (DomU) per bridge

b. trying to hide the NICs from Dom0 using something like "pciback hide" - (pointers/example of how one would do this in Centos 5.5 would be highly appreciated...)



Also, I have noticed that sometimes - somehow erratical since I can not replicate - it seems that VMs are timing out: while editing in vi it does not respond anymore.

Nothing in the logs, of course. And no indication in top either. Also, copying 8 GB of data from one disk to another takes 50 (fifty) minutes !!! - both LVMs attached

separately to the DomU as two independent volumes [xvda - /dev/mapper/VG1-VM1 and xvdb - /dev/mapper/VG2-VM1_home].


Would it be recommended to have all the storage in one block device - one xvda only - which will have its own LVM structure opposed to multiple xvd's?


Any suggestions on improving the performance in accessing block devices?


I am somehow baffled since I have read that XEN is used by ISPs which probably host tens of DomUs on a host machine, and I am struggling to host 7 VMs on a dual quad Xenon box with 48 GB RAM and 3TB RAID5 15K disk storage!


Please be gentle since I am rather new to XEN.






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