If a Site will be Temporarily Unavailable for Maintenance

[Martin]

Hi all,
i have 3 Sites on a dedicated host which will be unavailable for 24h. I can put an index.html and a htaccess file on an other host and for that time, to tell people that we will be back in 24h. But the other 5000+ Pages won`t be accessable for google this time. What Error-Header should i generate to prevent a rankingdrop?

I think 404 is best any suggestions?

100 => 'Continue',
101 => 'Switching Protocols',
200 => 'OK',
201 => 'Created',
202 => 'Accepted',
203 => 'Non-Authoritative Information',
204 => 'No Content',
205 => 'Reset Content',
206 => 'Partial Content',
300 => 'Multiple Choices',
301 => 'Moved Permanently',
302 => 'Moved Temporarily',
303 => 'See Other',
304 => 'Not Modified',
305 => 'Use Proxy',
400 => 'Bad Request',
401 => 'Unauthorized',
402 => 'Payment Required',
403 => 'Forbidden',
404 => 'Not Found',
405 => 'Method Not Allowed',
406 => 'Not Acceptable',
407 => 'Proxy Authentication Required',
408 => 'Request Timeout',
409 => 'Conflict',
410 => 'Gone',
411 => 'Length Required',
412 => 'Precondition Failed',
413 => 'Request Entity Too Large',
414 => 'Request-URI Too Large',
415 => 'Unsupported Media Type',
500 => 'Internal Server Error',
501 => 'Not Implemented',
502 => 'Bad Gateway',
503 => 'Service Unavailable',
504 => 'Gateway Timeout',
505 => 'HTTP Version Not Supported',

[bird]

As a visitor, I would find a "302 - Moved Temporarily" redirect to the homepage the most helpful. And I guess that it also causes the least harm with the search engines, as it basically tells them to check back at the original URL at some later time.

[bcc1234]

What is the expiration time for the zone ?
Most people use something like 48 hours so a large number of your visitors (and search engines) would still hit the old box.

Modify your DNS zone to expire in something like 5 minutes at least a week before.
That way you'll be able to change hosts quickly.

After you are done with the maintenance set it back to whatever you use now.

Btw, I think google uses it's own dns caching and the 24th seems like the worst time to take the server down.