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Re: [Xen-users] I need some answers please

To: inas mohamed <inas_2003@xxxxxxxxx>
Subject: Re: [Xen-users] I need some answers please
From: "Fajar A. Nugraha" <list@xxxxxxxxx>
Date: Tue, 8 Mar 2011 14:39:24 +0700
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On Tue, Mar 8, 2011 at 1:53 PM, inas mohamed <inas_2003@xxxxxxxxx> wrote:
>
> Hi,
> I am new to XCP, and I have some queries.

my comments below are generic to Xen, but should apply to XCP as well.

> 1. when I create a VM I am allocating memory for this one, my question is : 
> Is this memory is reserved to that VM even if it is down?

No

> and if yes how can I use this memory for another VM while it is down?

Just start another domU

> 2. If I have xen host with 12G RAM and I want to create 3 VMs on that host 
> what is the maximum value for RAM size I can use to leave enough memory for 
> the XEN host to work fine?

That depends.
When using bare RHEL dom0, I used to be able to run dom0 using only
512MB. Now that I have zfs on it, even 1.5GB doesn't seem enough.
CMIIW, I think XCP already limits how much memory the dom0 (you call
it "Xen host") will use, so from users' perspective you can just start
domUs until it complains not enough memory.

> 3.If many hosts joined a pool lets say 3 hosts each with 12G RAM and each one 
> has its local SR (no shared storage). Can I create a VM with more than 12G 
> RAM and specify a sr of one host for it?

Nope.

-- 
Fajar

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