“Load balancing error” – Issues with load balancing configurations in a SharePoint farm.

Troubleshooting “Load Balancing Error” in SharePoint Farm

Issue: SharePoint farm experiences performance degradation, request timeouts, or uneven server load distribution due to load balancing configuration issues.
Causes: Misconfigured load balancer settings, faulty health checks, session persistence issues, or uneven traffic distribution.

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1. Identify Load Balancing Issues

Before applying fixes, determine the root cause of the load balancing error.

Symptoms of Load Balancer Issues:

✅ Slow page loads or timeouts when accessing SharePoint.
✅ Users randomly being logged out or losing session data.
✅ One server handling most requests while others remain idle.
✅ HTTP 502, 503, or 504 gateway errors.
✅ SharePoint services failing intermittently.

Tools for Diagnosis:

🔹 Fiddler / Wireshark – Analyze HTTP requests and responses.
🔹 ULS Logs (C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\16\LOGS) – Check for load balancing-related errors.
🔹 Event Viewer (eventvwr.msc) – Look for network-related warnings/errors.
🔹 IIS Logs (C:\inetpub\logs\LogFiles) – Verify if requests are reaching all servers.
🔹 PowerShell – Check SharePoint server health:

Get-SPServer | Select-Object Name, Role, Status

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2. Check Load Balancer Health Checks & Server Availability

Load balancers monitor server health using periodic health checks. If a server fails, it may be removed from rotation.

Fixes:

🔹 Verify that all SharePoint Web Front End (WFE) servers are responding:

Test-NetConnection -ComputerName <ServerName> -Port 80

🔹 In Load Balancer Configuration, ensure that:

• The health probe URL points to a valid endpoint (e.g., /_layouts/15/healthcheck.aspx).
• All WFE servers are listed and active.
• The health check interval is set to an optimal value (5-10 seconds).
  🔹 Restart IIS to refresh configurations:

iisreset /noforce

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3. Ensure Session Persistence (Sticky Sessions) is Configured Properly

If session persistence is not enabled, user sessions may switch between servers, causing login issues or session timeouts.

Fixes:

🔹 Enable sticky sessions (affinity) in the load balancer settings.
🔹 For SharePoint authentication, configure Forms Authentication or Claims-based Authentication to maintain session integrity.
🔹 If using Azure Load Balancer, enable “Source IP Affinity”.

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4. Verify Load Balancing Algorithm & Traffic Distribution

Load balancers distribute requests using different algorithms. Incorrect configurations can overload one server while others remain underutilized.

Fixes:

🔹 Use Least Connections or Round Robin for evenly distributed traffic.
🔹 Monitor load distribution using:

Get-SPServiceApplicationPool | Select Name, Status

🔹 If using Windows Network Load Balancing (NLB), verify node status:

wlbs query

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5. Check Firewall & Network Settings

Blocked ports or misconfigured firewall rules can prevent servers from communicating properly.

Fixes:

🔹 Ensure the following ports are open between the Load Balancer and SharePoint WFEs:

• HTTP (80)
• HTTPS (443)
• SQL Server (1433, 1434)
• Central Admin (32843)
  🔹 Run telnet to test connectivity:

Test-NetConnection <WFE_Server> -Port 80

🔹 Check firewall logs for dropped or rejected requests.

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6. Optimize IIS & Web Application Settings

IIS misconfiguration can impact load balancing performance.

Fixes:

🔹 Verify host header bindings in IIS for SharePoint Web Applications.
🔹 Adjust IIS Application Pool recycling to avoid unnecessary session resets.
🔹 Increase the connection timeout:

Set-WebConfigurationProperty -filter "/system.applicationHost/sites/siteDefaults" -name "connectionTimeout" -value "00:05:00"

🔹 Enable HTTP Keep-Alive to reduce connection overhead.

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7. Optimize SQL Server Performance to Prevent Backend Bottlenecks

Slow SQL Server queries can delay responses and cause perceived load balancing failures.

Fixes:

🔹 Set max memory limits for SQL to prevent resource contention:

EXEC sp_configure 'max server memory', 12288;
RECONFIGURE;

🔹 Optimize SharePoint database performance:

• Rebuild indexes (ALTER INDEX ALL ON [TableName] REBUILD;).
• Reduce tempdb contention by increasing tempdb files.

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8. Monitor and Automate Load Balancer Performance

Regular monitoring helps detect and resolve load balancing issues before they impact users.

Fixes:

🔹 Configure Performance Monitor (perfmon.msc) to track server load.
🔹 Set up SharePoint Health Analyzer alerts for connectivity issues.
🔹 Use Azure Monitor / AWS CloudWatch for cloud-based SharePoint deployments.
🔹 Schedule regular log analysis using PowerShell:

Get-EventLog -LogName System -Newest 50 | Where-Object { $_.EventID -eq 10016 }

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