What causes Error 11027?

Quorum lost due to node failure. Storage paths disconnected. Cluster service dependency failure. Disk space or IOPS bottleneck

How do I fix Error 11027 (WSA_QOS_EPSFLOWSPEC)?

Check Cluster Health: Open PowerShell as Administrator. Run: Get-ClusterNode to check node status. Run: Test-Cluster for full validation. Review the HTML report for issues

Fix WSA_QOS_EPSFLOWSPEC — Windows Error Code 11027

Q: What is Windows Error 11027 (WSA_QOS_EPSFLOWSPEC)?

Error 11027 (WSA_QOS_EPSFLOWSPEC) is a Windows Cluster & Storage error that occurs when an invalid or inconsistent flowspec was found in the qos provider specific buffer.. This guide provides step-by-step solutions to resolve this issue.

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⚡ Quick Fix

Check Cluster Health: Open PowerShell as Administrator

👇 See all 1 solutions below

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📑 Table of Contents

What is Error 11027? Common Causes Step-by-Step Solutions Prevention Tips Related Errors

💡 What is Error 11027?

Windows System Error Code 11027, known as WSA_QOS_EPSFLOWSPEC, is a Cluster & Storage error that occurs during cluster, backup, and storage management. The error indicates that: An invalid or inconsistent flowspec was found in the QOS provider specific buffer. When this error is encountered, the Windows operating system was unable to complete the requested operation within the storage/cluster services subsystem. The error code 11027 is returned by the GetLastError() function and provides developers with a specific identifier to diagnose the root cause of the failure. The symbolic name WSA_QOS_EPSFLOWSPEC maps directly to this numeric code and is commonly referenced in Microsoft documentation, developer forums, and system logs. Understanding this error and its context within cluster, backup, and storage management is essential for effective troubleshooting.

⚠️ Common Causes

Quorum lost due to node failure
Storage paths disconnected
Cluster service dependency failure
Disk space or IOPS bottleneck

✅ Step-by-Step Solutions

1 Check Cluster Health

Open PowerShell as Administrator
Run: Get-ClusterNode to check node status
Run: Test-Cluster for full validation
Review the HTML report for issues

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💻 Diagnostic Command

Run this PowerShell command to find related events in your system log:

Get-EventLog -LogName System -Newest 20 | Where-Object {$_.Message -like "*11027*" -or $_.Message -like "*WSA_QOS_EPSFLOWSPEC*"} | Format-List

💡 Open PowerShell as Administrator, paste the command above, and press Enter.

🛡️ Prevention Tips

Configure redundant storage paths (MPIO)
Validate cluster after updates
Monitor disk latency and capacity

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Last updated: 2026-03-13

📖

Based on Official Microsoft Documentation

Solutions Tested on Windows 10 & 11

Error codes sourced from Microsoft Win32 SDK. Updated 2026-03-13.