Db2 Mirror for i Helps Clients Make Updates Without Downtime
IBMer Kris Whitney explains how a continuously available database helps industries where downtime is never acceptable.
Kris Whitney, product architect, Db2 Mirror for i, is photographed at IBM Rochester., Image by Bryce Johnson
By Scott McKinney09/01/2020
One of the greatest challenges facing IBM i clients today is downtime. Unplanned outages can cost organizations millions of dollars an hour. But the good thing for IBM i clients is the platform doesn’t have a lot of unplanned outages, where something crashes out of the blue.
“What really drove Db2® Mirror from a clients' requirements standpoint wasn’t unplanned outages,” says Kris Whitney, product architect, Db2 Mirror for i. “It was the planned ones, where you have to take the system down to apply a patch or maintenance.”
Db2 Mirror, released by IBM last year, delivers a continually available database for IBM i clients. Because it addresses a widespread pain point surrounding downtime, it’s seen unusually high adoption interest.
IBM delivered this enhancement in response to client feedback. Continuous availability should be the next step in clients’ high availability/disaster response plans, Whitney says.
The Price of Downtime
If you feel it’s unacceptable to go offline for maintenance windows, you’re not alone. The world has changed. Doing planned maintenance in off-hours is not as easy as it once was. “Planned maintenance was the original pain point that brought clients to request a continuous availability option,” says Whitney. “It was becoming unacceptable to the line of business to go offline an hour every month or quarter.”
There’s a financial and an operational efficiency price for downtime. The cost for an unplanned outage varies widely across industries. The median is around $300,000 to $400,000 for an hour of downtime. In the banking and finance industry, an hour of downtime can cost upward of $10 million. Planned outage costs are a little more complex to estimate because you can sometimes reduce the business impact by scheduling them off peak hours.
Some traditional industries can take Sunday afternoon offline and not have a business impact. But certain industries are having problems finding a window where their core business can go offline.
“The trick is to find out that price for an outage, and then examine how much you want to spend on your insurance policy to prevent these outages,” says Whitney. “If you can understand that up front, it’s easier to truly commit to a Db2 Mirror type implementation.”
The Need for Continuous Availability
Why is there such demand for continuous availability among IBM i clients? Because in most organizations where IBM i sits at the heart of the business, any outage causes financial constraints that dwarf the price tag of Db2 Mirror.
A large online retailer, has a global web presence that required continuous availability for everything from web servers to inventory. “This client was trying to develop more agile practices where you can introduce things, but you can also fail over if it doesn’t work correctly,” Whitney says. “They were on the forefront of pushing this active-active continuous delivery architecture a few years ago, so if a server fails, they could retry the other path and utilize it for both availability and also to get into a rolling upgrade type solution.”
That active-active architecture is the key difference between Db2 Mirror and its predecessor, PowerHA® SystemMirror. PowerHA is an active-passive implementation, so your applications are only running on one node. If you do failover, you have to shut down your applications and bring them back up. In an active-active database architecture, your applications can be active on both nodes. You’re redirecting traffic to one node instead of shutting down application layers. This improves operational efficiency by allowing maintenance to do rolling upgrades.
“On active-passive implementations, we’ve typically gotten it down to a 20-minute type time frame to do a switchover and bring your apps back online.” says Whitney. “In a Db2 Mirror switchover, it probably takes less than a minute to redirect traffic to the other node.”
Unexpected Use Cases
The Db2 Mirror project was client driven from the beginning. For example, feedback showed users wanted a button that mirrors everything on the system that’s capable of being mirrored. “We were hesitant to give them that capability, because we thought they might mirror too much, but we learned clients would rather mirror too much and tune it back, versus missing something,” says Whitney.
IBM continues to gather feedback from even more diverse clients than their original pre-GA group. And IBM is learning that some clients are using Db2 Mirror in unexpected ways.
An insurance industry client is trying to reduce planned maintenance windows. “They’re a sophisticated client, but it takes them about an hour to do a PowerHA® switchover,” Whitney says. “Whereas in a Db2 Mirror switchover, it will probably be less than a minute to redirect traffic to the other node.”
That will be an active-passive implementation, with a fast failover. They’ll run analytics on one node and use the second node to feed data to other servers.
A client in healthcare hosts software as a service for multiple hospitals. They’re working to use Db2 Mirror to do rolling upgrades of their software at different hospitals. They’ll use Db2 Mirror to keep the hospital online as they do the upgrade, then they’ll tear it down and move to the next hospital. Whitney is seeing interest from other business partners to offer a software upgrade service using that temporary Db2 Mirror scenario.
Whitney sees many clients in the financial industry that offer multiple services, but pick one to make into an active-active cluster. This could be a trading application or an ATM application. They may have business or government requirements to make those applications active-active.
Getting up and Running
Getting your applications running in a Db2 Mirror environment is fairly straightforward. The database is mirrored, but running your applications active-active needs consideration. “We knew from client feedback that they didn’t want to do a lot of application changes to use Db2 Mirror, and mostly that’s held up,” says Whitney. “We’ve had several companies get their applications running in a Db2 Mirror environment very quickly.”