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-users

Re: [Xen-users] What are the advantages of running domU in a lvm logical

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] What are the advantages of running domU in a lvm logical volume?
From: Freddie Cash <fjwcash@xxxxxxxxx>
Date: Thu, 10 Apr 2008 09:42:51 -0700
Delivery-date: Thu, 10 Apr 2008 09:44:19 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <1207835228.16944.71.camel@xxxxxxxxxxxxxxxxxxxxxxxx>
List-help: <mailto:xen-users-request@lists.xensource.com?subject=help>
List-id: Xen user discussion <xen-users.lists.xensource.com>
List-post: <mailto:xen-users@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=unsubscribe>
References: <1207835228.16944.71.camel@xxxxxxxxxxxxxxxxxxxxxxxx>
Sender: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: KMail/1.9.9
On April 10, 2008 06:47 am James Pifer wrote:
> I've built my second xen server using SLES10SP1. I learned quite a bit
> on the first server with help from this list. This second xen server is
> going to be used for hosting mostly windows domU's.
>
> I've followed the instructions here:
> http://ian.blenke.com/vmware/vmdk/xen/hvm/qemu/vmware_to_xen_hvm.html
> I've successfully converted two vmware images to xen domU's. It worked
> amazingly well!
>
> I have three questions.
>
> 1) The last part of instructions has you create a logical volume and dd
> the disk image to it. Based on my experience with the first server, I
> left a whole bunch of free space for doing this.
>
> But why do this? Why not just run the domU from the img file? I tested
> it on the ones I did and it seems to run fine. Just wondering if there
> are specific advantages for running from a logical volume.

Image files make things more portable (just copy the file around), but 
slow things down as you have a filesystem in a partition (domU) in a file 
on a filesystem (dom0) on a block device (phy).

LVM partitions make things less portable (you have to clone the partition 
instead of just copying a file) but speed things up as you just have a 
filesystem in a partition (domU) on a block device (phy).

Or something along those lines.

> 2) For a windows domU, if you restart dom0, is the domU shutdown
> gracefully? I clicked shutdown from virt-manager and it looked like it
> just "cut power".

Connect to the Windows domU via rdesktop or vnc and watch what happens. :)

> 3) What is a realistic expectation for how many domU's can run on a
> host? Obviously this is dependent on how they are being used, but if
> dom0 has two dual core xeons at 2.6 GHZ and 16 GB of RAM, could you
> conceivably run 5,6,or 7 windows servers with 2 GB of RAM each? (let's
> assume NOT high transaction servers)

I haven't benchmarked it yet, or run any real performance checks, but my 
rule-of-thumb so far has been to use 1 Ghz of CPU per VM and 768 MB of 
RAM per VM as a minimum.  So, personally, I wouldn't run more than 6 VMs 
on your system without doing some benchmarking to see how thing run.

I only have two Xen boxes setup up to date:
  * 2x single-core Opteron 2 GHz CPUs w/4 GB RAM (64-bit Debian Etch dom0) 
running 4 PV VMs all running 64-bit Debian Etch domUs (these are web, 
subversion, samba, and cups servers)

  * 2x dual-core Opteron 2 GHz CPUs w/8 GB RAM (64-bit Ubuntu Hardy) 
running a mixture of PV and HVM VMs running with various FreeBSD, Linux, 
and Windows domUs, with up to 7 running at a time (this is just a test 
server at the moment)

-- 
Freddie Cash
fjwcash@xxxxxxxxx

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users