RE: [Xen-users] Can we run more virtual machine than the memory avaible?

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Rachid Abdoun
> Sent: 22 June 2006 14:06
> To: Xen-users@xxxxxxxxxxxxxxxxxxx
> Cc: EHRENSBERGER Juergen
> Subject: [Xen-users] Can we run more virtual machine than the 
> memory avaible?
> 
> Hi,
> 
> I'd like to create a virtual network with xen who have more tha 20  
> hosts. Every host has 30MB in his configuration file. The total of  
> memory is
> 
> 20X30 = 600MB
> 
> +
> 
> 64MB for the dom0
> --------------------------
> = 664MB
> 
> but I only have 512MB on my workstation. Can this virtual network  
> possible with xen? Or you need to have enough ram!?

You need enough RAM. 

What you COULD do, assuming the GUEST OS supports it, is to reduce the
amount of RAM you give each guest, and let the guest swap to disk. 

The reason you can't overcommit memory from Xen's side of things is that
the Xen hypervisor doesn't actually know how (or what) to swap to/from
disk. This is, primarily, because we don't actually want Xen to do this
(since it wouldn't actually know which parts of memory the OS is using
for what...), but also because the hypervisor doesn't have a clue what a
hard-disk is - there's no drivers for any storage-device in Xen. 

--
Mats
> 
> Thank you
> 
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> 
> 



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