An Introduction to System i (AS/400) High Availability

Introduction
Every company faces critical hours when system downtime is unwelcome—whether it’s planned or unplanned. One company’s important hours might only be from 9-to-5, while for another it’s 24x7. Increasingly, shops that were able to accommodate some periods of downtime for backups and system maintenance are finding that this window is quickly shrinking (or has disappeared altogether) because of increased system demands—especially from global and online business. Because of the need to keep systems available for increasing amounts of time, companies are realizing that a system failure or a site disaster would create an enormous disruption and expense, especially if it went on for longer than a few hours. For many companies, exposure to this amount of potential downtime has become unacceptable. Shops that thought they weren’t candidates for a high availability solution are now realizing an urgent need to start looking at their options.
The purpose of this white paper is to provide an introduction to System i high availability for companies that want to understand this technology and evaluate whether such a solution can become a cost-justifiable component of their backup and recovery strategy.
Before looking at the details of System i high availability, lets take a quick look at the cost of downtime and some of the primary disaster recovery strategies that are used to mitigate this cost.

The Cost of Downtime
Management is often amazed when they add up all of the direct and indirect costs of what downtime costs their company. At first, they may figure that if a system is down for several hours or even a day, it is certainly a big inconvenience and a tolerable risk—as long this kind of downtime is a rare occurrence. However, once numbers are plugged into the following rule-of-thumb formula, they are often shocked:
Take the average sales lost during an hour of system downtime during business hours, then add the total hourly wage (including benefits) of all employees that are idle during that hour of downtime. Now multiply this figure by the estimated number of hours of system downtime during a year. Finally, multiply the result by 2 to take into account the costs of this lost employee productivity, lost business reputation, and lost business—both now and in the future—from your lost customers.

Unplanned Downtime vs. Planned Downtime
The IBM System i is considered the most reliable business system in the industry; some studies put its reliability at 99.95%. But consider the following from the IBM Redbook, Clustering and IASPs for Higher Availability on the IBM eServer System i Server: “According to one IBM study, the System i server averages 61 months between hardware failures. However, even this stellar record can be cause for availability concerns. Stated another way, 61 months between hardware failures means that nearly 67 percent of all System i servers can expect some type of hardware failure within the first five years.”
Other sobering statistics to consider:
- According to the Hurwitz Group, after the loss of a system for a week 43% of businesses never reopen and another 29% close within two years.
- According to Gartner, 93% of all companies that experience ‘significant data loss’ are out of business within five years.
Despite the potentially dire consequences of unplanned downtime, less than 10% of all downtime can be attributed to unplanned events, and only a fraction of that is due to a site disaster. The other 90+%—the kind that companies face on a regular basis—are those caused by system maintenance tasks, including:
- Data backups (nightly, weekly, and monthly saves)
- Reorganization of files—to reclaim disk space and improve performance
- Vendor software upgrades & data conversions
- IBM software release upgrades & PTFs
- New application software installations
- Hardware upgrades
- System migrations
Regardless of the cause of downtime, what matters most is reducing or eliminating the risk of downtime during critical hours of operation.

Disaster Recovery Strategies
For nearly 80% of companies in the small to medium range (SMB), their entire disaster recovery strategy consists of performing regular saves to tape. This usually includes periodic saves of their entire system, daily incremental tape saves of changed or otherwise critical data, and then storing these tapes safely offsite.