DR and HA 101. What those letters mean & why they’re important to almost every business

Pat Phelan Wrote my first “paid” program in 1975, written on an HP-25. Built and programmed microcomputers in the 1970s First commercial database was IMAGE-3000 on an HP 3000. Currently working with many databases on many platforms. Joined DECUS in the 1970s Regular user of Ward Christiansen’s CBBS Active in PASS Local Group Leader SQL Saturday Organizer Speak at SQL Saturdays 6-10 times per year

Disclosure: Pat Phelan works for Involta, LLC Disclosure: Pat Phelan works for Involta, LLC. But he isn’t here to sell you anything. Involta does: Co-location Your equipment in our data center Private Cloud seller We sell Vcloud and Hyper-V to clients Public cloud reseller Azure AWS Google We provide Managed Services Help desk System Admin Email “Last mile” cable/fiber in some areas of the country Staff augmentation Project/contract expertise

DR – Disaster Recovery This is what helps you (the DBA) get the business back up after a meteor destroys your office, data center, etc. DR has been around since shortly after the first disaster, probably in the 1960s For most businesses, having a valid (working) DR plan is the difference between recovering from a disaster or not.

HA – High Availability HA is an important “next step” for many businesses after DR is working HA has been around in many ways for years such as having multiple aircraft which can become “Air Force One” on very short notice. HA is implemented differently on computers than in other fields, but many of the ideas carry over well. If HA is perfect, a business may not need DR. Historically, it has always been a bad idea to bet on perfection.

DR preparation The first and most important step is to realize that your business needs a DR plan. The next step, is to understand what you need to protect from disaster. Attending this session is the first step in that process! DR is critical, it must be completed and maintained! HA is important, but it is harder to do well and much easier to make completely successful. Work on HA after DR is done!

DR and HA “Nines” The “Nines” expresses the percentage of availability One nine means 90 percent available. The system can have over a month of unplanned downtime per year Five nines means 99.999% available The system can have just over five minutes of unplanned downtime per year Each nine means changes to the system Nines quickly become EXPENSIVE $$$ Rule of thumb, adding each nine means ten times the previous cost

DR and HA Terms RPO and RTO RPO Recovery Point Objective (might be A or B) How much data can be lost? RTO Recovery Time Objective (might be B-G) How quickly does something need to be back online? RTP Return To Production (always G) A B C D E F G Normal Production Down Production Restored Secondary Online

DR and HA Terms RPO and RTO RPO Recovery Point Objective (might be A or B) How much data can be lost? RTO Recovery Time Objective (might be B-G) How quickly does something need to be back online? RTP Return To Production (always G) A B C D E F G Normal Production Down Production Restored Secondary Online

DR Requirements Backups, backups, backups!!! Identify “single point of failure” Power HVAC Telecom Storage Ask your providers about single points of failure Consider a consultant, experience and “fresh eyes” matter

DR Preparations Have a “getaway bag” and maintain it Keep “safe” backups When does a backup actually exist? Test your “safe” backups regularly (at least monthly) DR drills First one Start small Expect the first attempt to fail Subsequent drills Schedule when convenient As realistic as you can afford to make them

HA Planning Every HA plan has common elements, but no two are identical Even clouds have problems, they need HA too AWS and Azure have both had major outages in 2019 Your secondary should not share ANYTHING with primary If in doubt, hire a consultant who isn’t selling you anything but their services. In other words, don’t hire consultants from the company that provides your cloud to help you plan your HA

Pat Phelan DR and HA 101 Pat is the Database Mentor at Involta, LLC. Email: Pat@YetAnotherSQL.com Twitter: @YetAnotherSQL SQL Saturday #886 Indianapolis, IN August 2019