Storage Pool Capacity Threshold Exceeded – Real Fix
Your storage pool hit the capacity warning limit. The real fix is to free up space or expand the pool. I'll show you both.
You're seeing that warning—storage pool capacity threshold exceeded—and it's annoying because nothing seems broken yet. But if you ignore it, files stop saving. I've wasted hours on this myself. Here's the fix, no nonsense.
Immediate Fix: Free Space or Expand
Open Storage Spaces in Control Panel. Go to Control Panel > System and Security > Storage Spaces. Look at your pool. If it's above 70% used (or whatever threshold you set), you have two options:
- Free up space – Delete files you don't need. But if you're like me, you chose to expand.
- Expand the pool – Add more physical drives.
To expand: click Change settings (requires admin rights), then Add drives. Select an empty drive (same or larger size, but NOT smaller than the smallest drive in the pool). Hit Add. Done.
If Adding Drives Doesn't Work
Sometimes the option is grayed out. This happens when your storage layout (like Simple or Parity) doesn't support adding drives of a different size. What's actually happening here is Windows hides the add button if the new drive is too small. You need a drive at least as big as the largest drive in the pool. Get a matching drive.
Why the Warning Appears
The threshold you set (default 70%) triggers a critical event when pool capacity crosses it. Windows doesn't have a safety buffer—it alerts you at exactly that percentage. The error code 0x807800C5 means the pool's consumed space reached or exceeded this limit. It's not a failure, it's a nudge.
The reason step 3 works is that Storage Spaces uses a concept called slab allocation. It needs contiguous free space on physical disks to store new data stripes. When the pool is near full (especially in Parity setups), slabs are fragmented. Adding a new disk gives fresh contiguous slabs.
Less Common Variations
Thin Provisioning Pool Shows False Full
If you used thin provisioning (the default), the pool reports capacity based on logical allocation, not actual disk usage. You might see 90% full but only 50% of physical space is used. The fix: go to Storage Spaces > Change settings and increase the pool size limit (not the physical drives). It's a virtual cap.
Pool Shows Full After Replacing a Drive
You swapped a failing disk with a larger one. But the pool still says full. What's actually happening is Windows didn't automatically expand the volume to fill the new space. Right-click the volume in Storage Spaces and choose Extend volume. This tells Windows to claim the extra space. Takes 10 seconds.
Error on Server 2019 with ReFS
On Windows Server with ReFS volumes, the threshold can trigger at 80% even if you set it to 90%. This is a bug in ReFS's metadata allocation. Real fix: convert to NTFS (if possible), or set your threshold to 85% to give more headroom.
Prevention for Next Time
Don't wait. Set your threshold to 80% (not 70%) if you're on a tight budget. That way you get a warning but still have 20% room. Use a script to email you when pool size changes. Here's a PowerShell one-liner to check:
Get-StoragePool -FriendlyName "YourPoolName" | Select-Object Size, AllocatedSizeRun it weekly. If AllocatedSize/Size > 0.85, add a drive. That's it.
Pro tip: don't mix drive speeds (5400 RPM with 7200 RPM) in the same pool. The slowest drive drags the whole pool down.
Final word: storage pool warnings are your friend. They're not crashes. But they need a response. Add a drive or delete files. Don't ignore it or you'll wake up to a corrupted file system.
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