Vision Solutions Blog

Achieving Extreme Availability with MIMIX Active-Active Replication

May 24, 2017
  • HA/DR

Long gone are the days of relying solely on tape backup to recover your business on an IBM i server. Back then, restoring a server from tape could take at least a day or two--maybe more--and all data created since the last backup was lost. While it was inconvenient to be down and to re-enter the transactions since the last backup from paper records, it was the accepted service level.

Modern IT teams are faced with global customers and partners who require access to business systems around the clock, and they must often comply with strict regulations. If your systems aren’t online, customers can easily do business with someone else, and may never come back. In today’s competitive economy, the impact of downtime can be irreparable.

If your business relies on traditional solutions for high availability or disaster recovery that replicate data from a single production server to a backup server that stands ready to recover or restore operations in the event of failure or disaster, it’s time to assess whether your solution can restore operations quickly enough to meet the requirements of your customers, business partners and staff. If tolerance for downtime in your business has moved towards single-digit minutes or even seconds, you must move beyond conventional thinking.

Software-based high availability options for IBM i exist that go beyond the traditional expectations of recovery in tens of minutes. They replicate data between two or more active servers, each of which can run production workloads simultaneously, providing both workload balance across servers and HA/DR redundancy. This is known as “active-active” replication. No “recovery” is required to restore business operations—whether a server crashes or needs to be taken offline for maintenance. Instead, you can redirect users to another active server, which is fully in sync with the downed server, by simply switching IP addresses. The result is recovery time that can be measured in seconds.

The change to having two production servers capable of reading and writing the same business data concurrently requires a change to the way the database is accessed. Your high availability solution must shift from using positional replication, where row numbers are used to retrieve and write records, to keyed replication, where the database retrieves records based on a unique key pre-configured in the database (see below).

Active active Diagram

A collision resolution strategy must also be developed to address those events that can occasionally occur when two servers are actively reading and writing the same database, such as when the data in a row is updated simultaneously in multiple locations. A solid strategy includes application optimization to avoid collisions and the use of collision resolution methods to handle those that do occur.

It is important that your high availability solution provides methods to resolve conflicts and that your vendor works closely with you during an active-active implementation. Vision Solutions’ MIMIX Availability has supported Keyed Replication for active-active environments since the 1990s, allowing its customers to achieve unsurpassed high availability. A new white paper is now available to help you learn more about active-active replication, keyed replication and the rich set of collision resolution methods available in MIMIX.  Click here to download this informative paper now and begin planning how you can provide extreme availability for your ever-evolving business.