[Users] Node Stateless

[Mike Burns]

On Fri, 2012-06-08 at 23:03 +0200, Olivier Doucet wrote:
> Hi,
> 
> I wondered what is the progress on stateless node support in oVirt ?
> Page http://ovirt.org/wiki/Node_Stateless is not really updated.
> Is there a working iso to test ? What needs to be done ? And also,
> what would you need to move forward on this task ?

Hi Olivier,

This is currently still a work in progress.  I updated the wiki page a
couple weeks ago with the latest status (and haven't managed to do any
work on it since then).  

A basic summary:  stateless works, but with some limitations.

Limitations:

1.  No swap or overcommit.  We do not touch any disk at all, so there is
no swap available, and thus no overcommit possible with a stateless
node.
2.  No local storage domain -- not a big deal since most deployments
want shared storage of some sort, but same reasoning as #1
3.  Limited support from engine/vdsm.  This one is a bigger deal than #1
and #2.  engine doesn't understand the concept of a stateless node, so
it treats a stateless node the same as a stateful one.  This results in
the admin having to remove/re-add/re-approve the node on each reboot.  

All ISOs starting with 2.3.0 should have this support already.  You
simply need to add "stateless" (without quotes) to the kernel command
line at boot, along with other auto-install parameters to configure the
node and the host will be up and running.  

As for steps forward, we're currently focused almost entirely on getting
a node based on F17 working right now.  Once that is done and out the
door, we'll re-visit this feature.  

If you're looking to get involved, some of the functionality for solving
#1 and #2 is already available in the code.  Basically, what needs to be
done is add support in the TUI for AppVG and add some additional
handling around AppVG in auto-install.

As for #3, there isn't much left to do on the node itself, but we need a
decision from the engine and vdsm teams on how they want to handle this
long term.  There are a few ways to do it, all of which have their own
pros and cons.

Mike

> 
> Thank you !
> 
> Olivier
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