[badmash69]

In my experience , there are two kinds of deployment -- ones without DB changes and ones that are accompanies with DB changes.

The deployments that do not require DB changes are easy -- mirror the prod box(non db) onto a smaller box, , deploy upgrades/updates to prod box . If things go wrong, put mirror box online with a DNS/proxy configuration while apologizing to your customer who complain about slower performance .

When DB changes are involved , you need to have your DBAs do a dry run of backing out changes-- after all practice makes perfect. Communicate scheduled outage to customers, backup db . Mirror your production box. Roll put update -- if things go wrong, restore DB and bring the mirror box online.

I have always focused on DB aspect more -- loss of integrity of data can cause customers to look for your replacement.

But I am not sure if weekly upgrades of production environment with paying customers is advisable .