RE: [Xen-users] How many VMs/domains can Xen run?

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

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Rafa Grimán
> Sent: 02 November 2006 14:47
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-users] How many VMs/domains can Xen run?
> 
> Hi :)
> 
> Is there any "known" limit to the number of VMs/domains you 
> can run on Xen?
> 
> I know this depends on the hardware you've got: RAM, CPU, ... 
> It's just that 
> I'm interested in knowing if there's a known limit.

In a default build and without any changes to command-line, the heap that Xen 
uses to allocat it's internal data limits the number of domains to around 100 
in the 13 MB of heap that is default. It's perfectly possible to increase this 
by changing a constant in a header-file, but there are some side effects (that 
I don't quite remember what they are). In the 64-bit version(s) of Xen, you can 
even just throw on a command-line argument to increase the heap, but not in 
32-bit mode (because of said side-effects). 

[Speculation: I believe the side-effects is that more space is occupied by 
page-tables in each domain, so if you increase the size of the heap, each 
domain will have to have extra page-table-entries to get to the large sized 
heap, and thus each domain will in itself take up more space - but that's just 
what I think]. 

So, assuming we'd increased the size of the heap, the answer is really "As many 
as you can fit in your memory"... And if they are small, that could be quite a 
few!

--
Mats
> 
> TIA
> 
>    Rafa
> 
> -- 
> 50% of all statistics are inaccurate.
> 
> OpenWengo: rgriman
> 
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