Determining acceptable losses
We know that the PostgreSQL database will be offline at some point in the future. Maybe we need an upgrade to remove a critical security vulnerability or address a potential data corruption issue. Perhaps a RAM module is producing errors and needs immediate replacement. Maybe the primary data center was struck by lightning.
No matter the reason, we need to make decisions quickly. A helpful way is to ensure that the decision-making process is basing the answers on what the user expects for various levels of liability and on the context of the user. The QA department will not require the same response level as 10,000 shoppers who can't make a holiday purchase during a critical sale.
System outage and response escalation expectations are generally codified in a Service Level Agreement (SLA). How long should the maintenance last? How often should planned outages occur? When should users be informed and to what extent? Who is included in the set of potential database...
