Re: [Xen-users] 'xl reboot domid' ignores all in-memory changes AND the domu's config file changes

[Simon Hobson <linux@xxxxxxxxxxxxxxxx>]

Austin S. Hemmelgarn <ahferroin7@xxxxxxxxx> wrote:

A great description of self balloning and how to set it up. Not something I 
need, but very interesting to the geek in me ;-)

> 2. If you're doing this to overcommit memory (like I am), you need to have a 
> very good understanding of your workload's memory requirements and how 
> everything behaves, ...

I second this. it probably comes under the heading of "if you need to ask what 
the risks are, you shouldn't be doing it". Having seen the results of 
over-commit in disk storage and the hassles it causes, I don't think it's 
possible to stress too highly how big an issue it is when things ask for the 
resources you've promised them but don't have.
Fortunately, in the cases I've seen, it's been Windows HyperV and the 
hypervisor pauses all the VMs to prevent the train wreck that would otherwise 
happen. Still a PITA as the admin (not me !) has to find enough disk space to 
be able to unpause something and free up space within the virtual machine's 
disk - something of a catch 22 !


> Pretty much everything I know about it is stuff I've figured out from reading 
> source code.  What I've got above is as close to a complete description as 
> I've ever seen, maybe it should go on the Wiki?

I think it would be a very valuable wiki page.



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