A backup SLA promising “99.9% uptime” sounds like an incredible achievement until you find out what it means. Everything about how to assess SLAs from backup service providers is explained here. The gap between 99.9% and 99.99% seems negligible on paper – just one more digit – yet it amounts to a tenfold difference in reality.
What a Backup SLA Actually Promises (and Doesn’t)
When a vendor misses its SLA, the usual remedy is a service credit: a percentage of your subscription fee, not compensation for the business losses the downtime caused. Some SLAs also cap total credits regardless of how long the outage lasts, and many require you to file a claim yourself instead of crediting you automatically. Check the claim process and the cap before you need them.
Reading uptime percentages correctly
The table below shows how much downtime a backup SLA allows at each uptime level.
Scheduled maintenance is often excluded from this calculation
Many SLAs don’t count planned maintenance windows against the uptime percentage at all — meaning the practical, real-world availability you experience could be meaningfully lower than the headline number suggests, even when the vendor is technically meeting their stated SLA.
What happens when a vendor misses their SLA
An SLA guarantees a certain uptime percentage, and in case it is missed by the vendor, it ensures a certain compensation, usually in the form of a service credit. However, the SLA does not usually guarantee that you will be compensated for the financial losses arising from such downtime because the losses incurred are much more than the credit.
Questions to ask before signing an enterprise contract
- How is uptime actually measured, and by whom?
Self-reported uptime and independently monitored uptime aren’t the same thing — worth understanding which one a vendor’s SLA is based on.
- What specifically counts as “downtime”?
Scheduled maintenance windows are often excluded from the calculation entirely, which can make the practical availability meaningfully lower than the headline number suggests.
- What’s the actual remedy when the SLA is missed?
Usually a service credit — a percentage of your subscription fee, not compensation for your actual business losses from the downtime.
- Is there a cap on total credits, and who initiates the claim?
Some SLAs cap total credits regardless of how bad the outage was, and require you to proactively file a claim rather than crediting automatically.
Red Flags in Vague Backup SLA Language
Be wary of imprecise wording – an SLA that is not clear about how its percentages will be calculated, how downtime is excluded, or how the recovery process will be implemented is less likely to be usable than one that is specific, despite having a slightly smaller percentage.
Frequently asked questions
Q: Should an SLA be a major factor in choosing a backup vendor?
It’s one factor among several, not the deciding one. An SLA is more useful as a signal of a vendor’s confidence and architecture than as meaningful financial protection — the actual remedy rarely compensates for the real cost of downtime.
Q: Why do so many SLAs exclude scheduled maintenance from downtime calculations?
This is a common industry practice, and it’s worth understanding rather than being surprised by it later — a vendor with frequent, lengthy maintenance windows could have a technically impressive uptime percentage while still being unavailable more often than the headline number implies.
Q: Is a higher advertised uptime percentage always better?
Generally yes, all else being equal, but the difference between 99.9% and 99.99% matters more for some use cases than others. For most backup use cases, the difference is less consequential than the underlying reliability and how failures are handled when they do occur.
Q: What should I do if a vendor won’t share their SLA terms clearly?
Treat that reluctance as informative on its own — a vendor confident in their infrastructure and terms usually has no hesitation sharing the specifics directly and clearly.
Conclusion
When reading a backup SLA, specific language matters more than a headline percentage. An SLA without a clear measurement framework, a clear definition of what counts as downtime, and a defined process for resolving problems is riskier than a more specific SLA with a slightly lower percentage.
Priya Sundaram
Co-founder & CTO at Softyz Inc. Priya has spent 12 years building cloud security and backup infrastructure, and regularly helps enterprise customers read vendor SLAs beyond the headline percentage.