Xen under DICE

* network-bridge script can't handle our network setup (with multiple default routes). It barfs because it doesn't expect multiple default routes. Can edit the script to fix this.

* setting routing component to static and fixed g/w doesn't work either because network-bridge script does an ifdown during its run and then an ifup. At home, ifup will add the default gateway back, but on DICE it won't - you need to restart the routing component. A solution might be to start the xen system before the routing component.

* Don't see what the lcfg xen component gives you - I ended up just using the rc_xen script.

* Create a new VM (xen1) using virt-install :-

virt-install --name=xen1 --ram=1024 --file=/disk/scratch/xen1.img --file-size=20 --vnc --hvm --cdrom=/root/lcfg.iso --mac=00:16:3e:26:bd:12

* Add --nonsparse to above prepopulate the virtual disk for efficiency

* Connect to console using - /usr/bin/virt-viewer {name of Xen VM, eg xen1} or to serial console using xm console {name of VM}

* CD (for install) is /dev/hdc

* Need to use "serial" in boot CD

* /usr/sbin/xm create {vm name} - starts a VM up * /usr/sbin/xm console {vm name} - connect to serial console of VM (serialconsole.h works fine)

* Problem: can't find any way, other than recreating VM using virt-install, to reboot off the ISO image (or CD) if the installroot or installbase fails for some reason.

* Reboot of host doesn't cleanly shutdown the VM guests (prob can't get it to do this for HVM guests).

* Reliability woes - with one VM running, trying to create a new nonsparse image VM was sufficient to "panic" the whole host system

Tried Xen on top of a stock SL5.2 machine. Still get panics. Then Stephen suggested removing the watchdog from the grub config and hey presto things appear to be stable. Need to try with a DICE host now...

Install with 1 CPU and 2Gb = 36 mins Kernel build with 1 CPU and 2Gb = 58m (note 1 not 2 CPUs) Three simultaneous kernel builds with 1 cpu and 2Gb each took 68m each

Now trying Xen on top of DICE. This panics (but perhaps? less easy to provoke than before we took out the watchdog config). Wondering whether the panic always happens just when using virt-install (NOPE) Managed to have three VMs running simultaneously...... (UPDATE 19/01/09: looks like the panic is a known bug in Xen and is fixed in a new RHEL kernel. See https://bugzilla.redhat.com/show_bug.cgi?id=463500 for details)

Tried running on top of a bonded ethernet interface - need to explicitly tell Xen that you're using a bonded interface otherwise it goes direct to the physical interfaces (yuck). Do this by adding (network-script 'network-bridge netdev=bond0') to /etc/xen/xend-config.sxp

Tried running with VLANs on top of bonded interface. Looks like the stock Xen network scripts don't support VLANs at all - you have to write your own scripts from scratch to do this, and even then there are suggestions that this is buggy anyway...... In meantime, if want multiple interfaces will have to use real physical interfaces frown

Note - no way to cleanly shutdown (or suspend) an HVM VM guest from the Host.

Simon suggests making the LCFG installroot paravm aware and it might then be easier to install a paravm guest -see Debian

-- AlastairScobie - 12 Nov 2008

Topic revision: r14 - 30 Jan 2009 - 17:09:08 - AlastairScobie
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