How to avoid?

What is the best way to avoid site downtime as a result of moving your site from one server to another? A DNS change takes propagation time.

Before changing the DNS, make sure that you have the site duplicated at the new server. This will make the transition more seamless with less downtime. This does have a drawback though if you have an interactive site as some posts (such as in a forum) may go to the wrong server while the DNS is changing. But better than losing rankings and you can always temporarily shut off input from users until it's moved.

Now let’s talk for a minute about moving from mattcutts.com to someotherdomain.com. All other things being equal, I would recommend to stay with the original domain if possible. But if you need to move, the recommended way to do it is to put a 301 (permanent) redirect on every page on mattcutts.com to point to the corresponding page on someotherdomain.com. If you can map mattcutts.com/url1.html to someotherdomain.com/url1.html, that’s better than doing a redirect just to the root page (that is, from mattcutts.com/url1.html to someotherdomain.com). In the olden days, Googlebot would immediately follow a 301 redirect as soon as it found it. These days, I believe Googlebot sees the 301 and puts the destination url back in the queue, so it gets crawled a little later. I have heard some reports of people having issues with doing a 301 from olddomain.com to newdomain.com. I’m happy to hear those reports in the comments and I can pass them on to the crawl/indexing team, but we may be due to replace the code that handles that in the next couple months or so. If it’s really easy for you to wait a couple months or so, you may want to do that; it’s always easier to ask crawl/index folks to examine newer code than code that will be turned off in a while.

@ronit_3746, what zbigis what's to say is that he is moving his hosting provider and not domain.

and the best way as my suggestion is if site's a forum or something like that put a warning and stop posting for 2-4 hrs, and also keep a copy already duplicated before changing DNS.

DNS updates takes not more then that. when DNS update complete remove warning.

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If its a dynamic site like a Forum , Blog or a topiste list I think best way is down the site first and move it so you won't miss anything visitors might leave.

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