When you see "The IO operation at logical block address # for Disk # was retried" in your Windows Server System event log, it indicates a temporary storage subsystem issue that was automatically recovered through MPIO's retry mechanism. The key points about this message:

• Logical Block Address (LBA): Specifies the exact sector location where the operation failed
• Disk Number: Identifies which physical or virtual disk encountered the issue
• Retry Status: Confirms MPIO successfully reattempted the operation

Contrary to initial concerns, this message does not indicate data loss. The Windows storage stack employs multiple safeguards:

// Simplified view of Windows storage retry logic
if (IOOperationFails(firstPath)) {
    queueForRetry(operation);
    if (hasAlternatePath()) {
        attemptViaMPIO(alternatePath);
    } else {
        waitAndRetryOriginalPath();
    }
    logEvent(EventID 129); // The retry message we're examining
}

In my experience with blade servers, these retries typically occur during:

To properly diagnose these events, consider implementing this PowerShell monitoring snippet:

# Monitor MPIO retry events in real-time
Get-WinEvent -LogName System -MaxEvents 1000 | 
Where-Object {$_.Id -eq 129} |
ForEach-Object {
    $xml = [xml]$_.ToXml()
    $lba = $xml.Event.EventData.Data[0].'#text'
    $disk = $xml.Event.EventData.Data[1].'#text'
    Write-Host "Retry detected on Disk $disk at LBA $lba (Time: $($_.TimeCreated))"
}

While individual retries have minimal impact, frequent occurrences may indicate:

• Suboptimal MPIO load balancing policy
• SAN fabric congestion points
• Missed storage array thresholds

For critical systems, I recommend implementing performance counters to track retry rates:

# Create a custom counter for MPIO retries
$counterParams = @{
    CounterName = '\MPIO Retries(*)\Retries per second'
    SampleInterval = 5
    MaxSamples = 720
}
Get-Counter @counterParams -Continuous | 
Export-Counter -Path "C:\PerfLogs\MPIO_Retries.blg" -FileFormat BLG

When working with Windows Server 2012+ MPIO configurations, you'll occasionally encounter these warning entries in the System event log during path failures. The key components of the message are:

Event ID: 153
Source: Disk
Message: The IO operation at logical block address (LBA) 0 for Disk 7 was retried.

This message indicates that:

• The storage stack detected an I/O failure on the primary path
• MPIO successfully retried the operation on an alternate path
• The operation completed successfully after retry (otherwise you'd see a critical error)

For write operations specifically:

if (operationType == WRITE) {
    // The Windows storage stack guarantees:
    // 1. Either the full write succeeds on alternate path
    // 2. Or the entire operation fails with error status
    // No partial write or data loss occurs
}

You can query these events programmatically using PowerShell:

Get-WinEvent -LogName System | 
Where-Object { $_.Id -eq 153 -and $_.Message -like "*retried*" } | 
Select-Object TimeCreated, Message

For storage monitoring systems, you might want to filter these events when they occur during known maintenance windows:

# Example filter for known maintenance period
$events = Get-WinEvent -FilterHashtable @{
    LogName = 'System'
    ID = 153
    StartTime = [datetime]::Now.AddHours(-1)
    EndTime = [datetime]::Now
} | Where-Object {
    $_.Message -notmatch "Disk 7" # Exclude expected test disk
}

While these warnings are generally benign during path failovers, they warrant investigation when:

• Occurring outside of maintenance windows
• Accompanied by application timeouts
• Showing increasing frequency over time