IBM i Restore Time and RTO Calculator
Most AS/400 shops can tell you the backup schedule but not how long a full recovery would take. This calculator turns your restore speed and data size into a recovery time you can compare with the business requirement.
Your numbers
Measure from a real restore test. Tape drive speed, number of drives and parallel restore jobs all change this.
Hardware access, install of Licensed Internal Code and IBM i, then user profiles and configuration.
Receivers since the last full save, if you recover to a point near the failure.
Your results
Estimates only. Run a full restore test to a spare partition or recovery site before relying on any figure.
Total recovery hours vs restore throughput
Sweeps Sustained restore throughput from 100 to 1000, holding your other inputs fixed.
Recovery test plan review
Optional: have an expert review your IBM i recovery test plan.
Optional. The tool and every export work without this. No spam.
How to use it
Enter the data volume you would need to bring back for the business to run, not the whole disk. Use a restore throughput measured in a test, because tape specifications overstate real speed when files are small or when many objects are restored sequentially. Add setup time for hardware, installing the operating system and restoring user profiles and security.
The method
Total recovery time is setup plus data divided by restore rate, plus journal volume divided by apply rate, plus verification time. The tool also solves backwards: given your recovery time objective, the throughput you would need is data divided by the time left after the fixed steps. The chart shows how total time falls as throughput rises, with sharply diminishing returns above a point.
- Restoring libraries in parallel jobs can raise throughput if you have enough drives or a virtual tape library
- Large numbers of small objects restore slower than a few large ones
- Journal apply is often slower than people expect
How to read it
If you miss the objective, look first at the setup and verification terms, which are often padding for no good reason, then at throughput. If the needed throughput is above anything your hardware has ever done, the answer is a different architecture, such as replication to a second system, not faster tape. A negative margin should be taken to management as a gap with a price.
Common mistakes
Assuming the vendor's rated speed is what you will get, forgetting the time to find and mount media, leaving out the time to restore security data and authorities, and never testing. Also confirm that offsite or cloud backups can be retrieved at the rate you assume; a slow network link can dominate the whole calculation.
Frequently Asked Questions
What is the difference between RTO and RPO?
RTO is how long the business can be without the system. RPO is how much recent data it can afford to lose. This calculator focuses on RTO, with the journal step standing in for how close to the failure you recover.
Is this only for a full system loss?
It models a full recovery. For a library or file restore, use only the relevant data size and set setup to zero.
Does it apply to cloud-hosted IBM i?
Yes, but use the restore throughput that your provider's backup service achieves and add any time to request restores. Ask for their tested figures.
How often should I test?
At least once a year and after major changes in data volume, hardware or backup software. An untested restore time is a guess.
If you want a recovery test plan written for your IBM i environment, Netray can help you structure it and review the results.
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