When it comes to site moves, if you pick some URLs and not all, it can cause issues for Google. In short, moving all your URLs from one place to another will result in a much faster site migration than taking portions of your site to migrate at a time. But if you leave some URLs on the old domain, that will cause issues and slow the migration down in Google’s systems.
John said this at the 12:38 mark into this mornings video hangout. He said “If you’re keeping pages on the old domain that are not redirecting, then that’s something that will confuse our systems.” “It’s really just like keeping things on the old domain that’s something which I would try to discourage as much as possible,” he said.
In short, move all your URLs over all at once, Google will pick that up much faster than doing partial migrations.
Here is the video followed by the transcript:
If you’re keeping pages on the old domain that are not redirecting, then that’s something that will confuse our systems. Because when we crawl and index your website and we run across those pages then we start to question whether or not this is actually a site move. And then it essentially goes from being and move from one domain to another where or you can just like transfer everything to the new domain, it becomes a situation where you’re splitting a domain. You’re taking one domain, you’re keeping some things there and moving something somewhere else. And from our point of view that becomes a lot harder to process. That essentially means we have to reprocess both of these domains. And see like well what is this new website and what is on this other website that we already know about and how does the content kind of interact with with itself there.