Re: Running while upgrading -- Follow-Up

["Arvid Grøtting" <arvidg_(_at_)_netfonds_(_dot_)_no>]

Jacob Meuser <jakemsr_(_at_)_jakemsr_(_dot_)_com> writes:

> If you're worried about downtime, then why are you wanting to do
> something the unsupported, undocemented-except-on-the-maillist way?

There is another quite supported way, strictly speaking undocumented
except here:

- Do a fresh install on a new machine, with a temporary IP address.

- Copy the data (in this case, web pages, etc.) and supporting
  additional software onto the new machine.

- Test the new machine

- Shutdown the old machine and change the IP address on the new
  machine to that of the old, OR

- Leaving the old machine running, change dns so that the hostname
  previously used by the old machine points to the new one.

The second alternative only works if you can have both servers running
in parallel for a while while the dns changes propagate; this depends
on your application.  If it works, you'll have no downtime at all.

The first alternative will have an ARP cache timeout's worth of
downtime.

This is more expensive, yes, but after 1.5 years (since 2.9), you'll
probably want a hardware upgrade anyway, and if you don't, you only
need one spare machine to do this to several hosts (serially).  On the
upside, this method gives you the opportunity to test your application
on the new version *before* committing to it.  And seriously, if you
can't afford the downtime, you _can_ afford the hardware and you
_must_ have a spare anyway.

-- 

Arvid