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Re: [Xen-users] How many guest hosts per physical host

To: svarghese <vargh@xxxxxxxxx>
Subject: Re: [Xen-users] How many guest hosts per physical host
From: "Fajar A. Nugraha" <fajar@xxxxxxxxx>
Date: Sat, 19 Dec 2009 03:51:32 +0700
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On Wed, Dec 16, 2009 at 11:39 AM, svarghese <vargh@xxxxxxxxx> wrote:
> Can I create more than 16 guest hosts in my physical host?

Xen supports running a lot of domUs. Last time I experiment with this
I was able to start over 300 PV domUs with 16 MBs memory each. At that
point xenstored uses lots of CPU, and starting another domU takes some
time, so I stopped it there. Note that I use LVM on dom0 as domU's

If you're looking for maximum number of SUPPORTED domUs, you should
ask your linux vendor (if you're using bundled Xen).

In your particular setup, you'd most likely be memory-bound, so the
answer would be NO. Not if each domU uses 1 GB. You need to reduce the
ammount of memory for each domU. dom0 needs some memory for itself, so
you can't allocate all 16GB for domUs.

> If the total
> number of host with 1GB RAM each exceeds 16, does XEN have any feature to
> mange the memory efficiently so that  memory will be allocated to guest host
> based on the load on guest hosts at a particular point of time?

Not by default. You can try


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