b) set up a second server on a different IP address and update the nameservers. (Not all clients will notice immediately because DNS can be cached.)
It's probably worth pointing out that it's not uncommon for DNS servers to have fairly long caching periods. My domains usually have a TTL (time to live) of 24-48 hours. This is because DNS records are mostly static.
I've seen hosting providers set TTLs of a week, which seems to me a fairly underhanded attempt to minimise churn.
-- Pete -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html
