[libvirt] [PATCH] Add documentation about migration.

[Daniel P. Berrange]

On Wed, Oct 26, 2011 at 12:46:42PM -0600, Eric Blake wrote:
> On 10/24/2011 07:50 AM, Daniel P. Berrange wrote:
> >From: "Daniel P. Berrange"<berrange at redhat.com>
> >
> >This adds a page documenting many aspects of migration:
> >
> >  - The types of migration (managed direct, p2p, unmanaged direct)
> >  - Data transports (native, tunnelled)
> >  - Migration URIs
> >  - Config file handling
> >  - Example scenarios
> 
> Sounds very useful.  The graphics generally look reasonable.
> 
> >
> >diff --git a/docs/migration.html.in b/docs/migration.html.in
> >index ee72b00..4a16162 100644
> >--- a/docs/migration.html.in
> >+++ b/docs/migration.html.in
> 
> I don't have this file in libvirt.git.  Did you forget a
> pre-requisite patch, or fail to squash two patches into one?  It's
> making it hard to review.  I created a dummy version, if only to
> test all the subsidiary pages.


Urgh, yes I meant to squash 2 patches together but forgot :-(


> >+      very large RAM sizes, which dirty memory pages quickly. On the deployment side, tunnelled
> >+      transports do not require any extra network configuration over and above what's already
> >+      required for general libvirtd<a href="remote.html">remote access</a>, and there is only
> >+      need for a single port to be open on the firewall.

> Also, should we mention "migration to file" (aka virsh save), or is
> that pushing the boundaries of what this page was intended to cover?

No, I consider that out of scope. This is just for cross-host
migration


> >+<h3><a id="flowpeer2peer">Managed peer to peer migration</a></h3>
> >+
> >+<p>
> >+      With<em>peer to peer</em>  migration, the libvirt client process only
> >+      talks to the libvirtd daemon on the source host. The libvirtd daemon
> >+      will then connect to the destination host libvirtd and controls the
> 
> s/host libvirtd and/host libvirtd, which/

No, because that implies the dest host will control migration. Even my original
text was ambiguous in this respect, so I rewrote this block.

> >+      will continue uninterrupted until completion.
> >+</p>
> >+
> >+<p>
> >+<img class="diagram" src="migration-managed-p2p.png" alt="Migration peer-to-peer">
> 
> This image is wrong.  It shows the client talking to the
> destination, when in reality, the client only talks to the source,
> and the source talks to the destination.  That is, your diagram
> looks identical to migration-managed-direct.png, although I don't
> think you intended it to be that way.

Yep, saved over the top of the file :-(

Daniel
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