windows_exporter/docs/runbooks/windowsclustersharedvolumealmostfull.md

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WindowsClusterSharedVolumeAlmostFull

Meaning

The Cluster Shared Volume shared_volume has less free space than the configured threshold for 15 minutes. The warning fires below diskFreeWarningThreshold (10 percent by default) and the critical alert below diskFreeCriticalThreshold (5 percent); both fire below the critical threshold, so inhibit the warning in Alertmanager. The alert needs the mscluster collector and fires once per reporting node, named by the instance label. sharedVolumeSelector excludes the ClusterPerformanceHistory volume of the cluster's own health history.

Impact

Virtual machines and databases on the volume cannot grow their files. Dynamic virtual hard disks pause the virtual machine when the volume is full, Hyper-V checkpoints and backups fail, and SQL Server stops writing.

Diagnosis

1. Compare windows_mscluster_shared_volumes_free_bytes and windows_mscluster_shared_volumes_total_bytes over the last days to see whether the volume fills steadily or filled suddenly.

2. On a cluster node, find the large files on the volume:

   Get-ClusterSharedVolume | Select-Object Name, @{n='FreeGB';e={[int]($_.SharedVolumeInfo.Partition.FreeSpace/1GB)}}, @{n='SizeGB';e={[int]($_.SharedVolumeInfo.Partition.Size/1GB)}}
   Get-ChildItem 'C:\ClusterStorage\<volume>' -Recurse -File | Sort-Object Length -Descending | Select-Object -First 20 FullName, @{n='GB';e={[int]($_.Length/1GB)}}
   

3. Look for leftover checkpoints (.avhdx files), orphaned virtual hard disks, backup snapshots that were not cleaned up, and dynamic disks that grew.

Mitigation

Delete or merge checkpoints, remove orphaned files, move virtual machines to another volume with storage migration, or extend the volume on the storage array and then in the cluster with Resize-Partition. Confirm free space is above the threshold. Raise the thresholds only for volumes whose growth is known and planned.