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Re: [Xen-users] Xen save takes a long time

To: Jonathan Tripathy <jonnyt@xxxxxxxxxxx>
Subject: Re: [Xen-users] Xen save takes a long time
From: "Fajar A. Nugraha" <fajar@xxxxxxxxx>
Date: Mon, 28 Jun 2010 07:42:27 +0700
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On Mon, Jun 28, 2010 at 4:48 AM, Jonathan Tripathy <jonnyt@xxxxxxxxxxx> wrote:
> Hi Everyone,
> By default, when I shutdown my Xen host, the system will try and save every
> DomU. I currently only have one DomU in my Xen host, however this takes
> about 7 minutes to save. Since this system will eventually go in a colo
> facility, and will host tens of customer VMs, waiting that kind of time
> isn't an option.
> Can some please:
> a) Explain why the DomU takes so long to save? Is this normal? The DomU has
> just a small 3G LVM disk which has hardly been used

How much memory does it have? 4G? "xm save" involves saving domU's
memory to dom0's disk. You could monitor disk activity on dom0 using
"iostat -mx 3" (or whatever tool you like). If it shows 100% disk
utilization during domU save, then the bottleneck is your disk.

> b) Is it safe, in a hosting environment, to disable guest "saving" on Dom0
> shutdown, and just resort do guest "shutdown"?

That's what I do on my production systems.


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