[mdlug] Server maintenance

[Adam Tauno Williams]

On Fri, 2012-11-16 at 17:46 -0500, Jay Nugent wrote:
> On Fri, 16 Nov 2012, Carl T. Miller wrote:
> > s/propagating/promulgating/
> > ; -)
> > On 11/16/2012 05:38 PM, Mat Enders wrote:
> >>  Hello all I will be taking down the MDLUG web and email server within the
> >>  next ten minutes.  I hope to have it back up with 2-3 hours.  This going
> >>  to
> >>  involve a change to DNS so part of it will be that propagating.
>     DNS *NEVER* propogates.  You plan ahead, reduce the TTL/Expire to just 
> a couple hours.  Once that *old* TTL has passed, begin your maintenance. 
> Sheesh!  I teach this basic stuff every day yet see this mistake over and 
> over and over...

This (a) assumes your DNS provider allows you to adjust the TTL and (b)
doesn't really deal with clients who cache look-ups on their own and pay
no attention to TTL values.

I think people generally use "propagate" to indicate the amount of time
it takes for clients to realize the change.  And I generally double the
expected time when telling anyone else how long it will take.