What are considered the best practices when putting your site in maintenance during an update? I'm asking because i'm not very fond of having a site with over 60k indexed pages in google throwing a 404 header actually telling Google that the sites has disappeared. I'd rather tell google that the site is gone for a few hours so the googlebot should come back after a few hours and do nothing for now.
Just found this blogpost on the official Google webmaster blog: http://googlewebmastercentral.blogspot.com/2011/01/how-to-deal-with-planned-site-downtime.html, straight from the source!
It should be acceptable to use a rewrite or other redirect to push all traffic to a maintenance page which returns a status 503 - Service Unavailable. From the W3, a 503 should be used when:
The server is currently unable to handle the request due to a temporary overloading or maintenance of the server.
See http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.5.4 for more information about the 503 status code.