Re: [Xen-users] iSCSi on Xen (with SuSE 10)

["Hubertus A. Haniel" <hubba@xxxxxxxxxxxx>]

On Sun, 01 Jan 2006 22:52:48 -0500, Alvin Starr wrote
> I have had good and bad luck with all the initiators but Core-iSCSI and 
> I have not yet gotten that one to work.
> Currently I am having the most luck with open-iscsi It seems to give the 
> best  in terms of being able to pick and choose what target I connect 
> to. The one issue with open-iscsi is that it seems to use up lots of 
> kernel memory.  If I connect more then 3 targets I run out of memory on 
> my Dom0 that is only configured with 256M.
> I have a 2.0.x version of xen running for nearly a year now with 
> linux-iscsi but I was never able to recreate the config with more 
> current versions of Xen.
> I have my DomU's running using the drives as visable in the Dom0. My 
> reason is that I believe that running through the block interface should 
> be much faster than running over the bridging network connection.
> The biggest issue with using the devices in Dom0 is making sure that the 
> iscsi devices are available using predictable device names. To get this 
> to work I have hacked the udev code to create the devices with a name 
> that matches the target name as set up in iet.
> 
> I tried booting a Dom0 from an iscsi drive using grubs network boot 
> capability but that did not work very well so I gave up doing that.  I 
> have had some luck booting a regular system using syslinux but had to 
> hack the initrd so badly that I just gave it up as being unsupportable.  
> If the open-iscsi guys manage to get iscsid to be restartable it may be 
> worth taking another look at that process again.
> 
> I have managed to migrate domains from my various xen servers so long as 
> the iscsi devices were available with the same device names on each server.


Would it be possible for you to explain or point me on to some documentation on
how you get a DomU to run on iSCSI? - I am trying to get this to work with SuSE
10.0 at the moment with the open-iscsi and iscsitarget that is shipped as part 
of
the distribution. - I think I have the iSCSI bit working fine and I have put the
device in a volume group and I have created logical volumes on it which I want 
to
use as backing devices for DomU. 
lvscan shows:
  ACTIVE            '/dev/datavg01/vm01lv' [2.50 GB] inherit
  ACTIVE            '/dev/datavg01/vm01swaplv' [512.00 MB] inherit
I do have to activate the volumes manually with "lvchange -a y" at the moment on
which is not too much of a problem as afterthat I can access the volumes fine.
I have created a root filesystem in the volume but when I activate the domain I 
get:

Waiting for device /dev/sda1 to appear:  ok
rootfs:  major=8 minor=1 devn=2049
Mounting root /dev/sda1
mount: No such device
Kernel panic - not syncing: Attempted to kill init!

I think I may be using the wrong kernel module within DomU - any ieas what I
should be using?

The contents of my domain config file in /etc/xen are:
kernel = "/boot/vmlinuz-xen"
ramdisk = "/boot/initrd-xen"
builder='linux'
memory = 256
name = "vm01"
cpu = -1
vcpus = 4
nics=1
vif = [ 'bridge=xenbr0' ]
disk = [ 'phy:datavg01/vm01swaplv,sda1,w',
         'phy:datavg01/vm01swaplv,sda2,w' ]
root = "/dev/sda1 ro"
extra = "3"
restart = 'onreboot'

What I am trying to archive at the end is domain migration from on Xen host to
another so any documentation of this on iSCSI would be very helpful.


Best regards
Hubba






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