Proving backups actually restore
A backup that has never been read back through a restore is a theory, not a guarantee. Osiris treats "backed up" and "proven restorable" as two different, separately-shown states, and a backup without a verified restore is shown as not done, not as a quieter shade of success.
What's checked today
A weekly sampled recovery-readiness check runs per mailbox and OneDrive: Osiris actually restores a sample and compares it back, then shows the result plainly as a sample-based check, not as complete coverage it hasn't earned. Where a check fails, that failure shows up in the mailbox or OneDrive's own status: it does not get averaged away into an overall green dashboard.
What's in development
Full test restore into a separate target, and verifying every backed-up item rather than a weekly sample, is actively being built. Until it ships, the sampled check is the honestly-labelled interim state. See theroadmap for exact status, andhow Osiris is built for the release checklist a version has to pass before this claim is made about it at all, including a full backup-and-restore run with a byte-for-byte hash comparison before any tag ships.
Frequently asked
How does Osiris verify that a backup can actually be restored?
By restoring it and checking, not by assuming a successful backup job means the data is recoverable. Today that runs as a weekly sampled recovery-readiness check per mailbox and OneDrive, shown as a sample rather than a full guarantee. Full, complete-coverage restore verification for every backed-up item, restoring into a separate target automatically, is in development. See the roadmap.
What happens if a verification check fails?
It's shown, not hidden. The affected mailbox or OneDrive's recovery-readiness status reflects the failure immediately, the same honesty rule that applies to Graph throttling waits and every other known limit in the product.
Is an unverified backup shown as successful?
No. A backup that hasn't been confirmed by an actual restore is treated, and displayed, as not proven, never quietly rounded up to "done."