The 2019 Org Chart Strikes Back: A Copilot Hallucination Story
An anonymised account of what happens when Copilot grounds in a stale tenant — and what the post-mortem revealed about the cleanup we should have done first.
If your Microsoft 365 storage bill jumped this year and you can’t explain why, the culprit isn’t your end users behaving badly.
It’s the way SharePoint and Teams retain content by default. Five quiet drivers account for most of the bloat.
None of them show up in your monthly Microsoft invoice — but all of them appear in any decent storage scan.
When Teams meetings are recorded, the video lands in the recorder’s OneDrive (for personal calls) or in the meeting channel’s SharePoint site (for channel meetings).
They’re typically 20–500 MB each. A 500-person company averaging two recorded meetings per week generates about 4 TB of Teams recording over a year.
Watch-rate data from Microsoft’s own telemetry says fewer than 18% of recordings get a second view. The rest sit forever, billed monthly.
Every SharePoint document library tracks version history by default.
Major edits create major versions; small ones can create dozens of minor versions.
A 50 MB PowerPoint with 20 versions is 1 GB on disk.
Microsoft 365 Archive doesn’t help here — versions live with the active file. Capping major versions to 10 (and minor versions to 0 for non-Office files) typically reclaims 12–18% of total storage on its own.
A SharePoint site needs at least one owner to be governable.
When the owner leaves, the site doesn’t disappear; it just becomes orphaned.
In the Contoso demo workspace we built, 102 of 200 sites had no owner — over half. Real tenants are usually 25–40%.
Orphaned sites are the largest single category of “reclaimable but politically tricky” storage: nobody knows what’s in them, so nobody wants to delete them. A scan that produces an inventory and asks each potential owner to claim or release is the cleanest path.
Two patterns drive this.
First, the file-attached-to-an-email-then-saved-to-three-places pattern — Sales saves it to their site, Marketing saves it to theirs, the proposal lives in OneDrive too.
Second, the template-copied-across-sites pattern — every project site starts from a copy of the master, including 80 MB of unchanged template files.
Duplicate detection at the hash level usually surfaces 5–8% of total storage as redundant.
SharePoint and Teams aren’t built to be your video CDN.
They’re billed like a database. When marketing uploads a 4 GB conference recording to a SharePoint library because it’s where Marketing keeps things, you’re paying database-tier prices for video-tier content.
The optimisation is straightforward: move large media to Stream (free, included) or to Azure Blob Storage (at $0.0184/GB/month, roughly 11× cheaper than SharePoint overage).
A 32 TB tenant with all five hogs running unchecked is paying about $66,000 a year in overage.
A focused 25% reduction — about what TSO underwrites — clears $17,000 of that off the bill, and the reduction holds because the underlying behaviours don’t snap back overnight.
Storage savings have a half-life of about 18 months in our data; that’s three quarters of clean billing before maintenance kicks back in.
The first step is knowing where the bytes are. Anything past that is operational discipline.
An anonymised account of what happens when Copilot grounds in a stale tenant — and what the post-mortem revealed about the cleanup we should have done first.
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opilot grounds its answers in your tenant’s content — and the content is full of contradictions, duplicates, and zombie data. Here are the five patterns we see in every scan that turn Copilot into a confident misinformer.
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