Solved: Why is “net use” so much faster than “Get-SmbMapping”??

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🚀 Executive Summary

TL;DR: The PowerShell cmdlet Get-SmbMapping is significantly slower than the legacy ‘net use’ command for querying network drive mappings due to its reliance on WMI/CIM for rich object output. To resolve this, engineers can use Get-CimInstance with Win32_MappedLogicalDisk for a balance of speed and PowerShell objects, or parse ‘net use’ output for maximum performance.

🎯 Key Takeaways

Get-SmbMapping’s performance bottleneck stems from its modern PowerShell CIM/WMI architecture, which involves more overhead to gather and instantiate rich objects compared to ‘net use’s direct, text-based API call.
The recommended solution for a balance of speed and PowerShell-native objects is to use ‘Get-CimInstance -ClassName Win32_MappedLogicalDisk’, which leverages an optimized WMI provider.
When using Get-SmbMapping is unavoidable (e.g., for unique properties like ‘Encrypted’), optimize its usage by employing ‘Select-Object’ early in the pipeline to reduce memory footprint and processing load for subsequent cmdlets.

Struggling with slow Get-SmbMapping performance in PowerShell compared to the legacy net use command? This post dives into the technical reasons for the speed difference and provides three practical, performance-oriented solutions for querying network drive mappings efficiently in your scripts.

The Problem: Why is Get-SmbMapping So Slow?

As a DevOps engineer, you live and breathe automation. You’ve embraced PowerShell for its object-oriented power and extensibility. But then you hit a snag with something that should be simple: checking mapped network drives. You run PowerShell’s modern cmdlet and notice a significant delay, while the old command-line tool is instantaneous.

Symptoms

The issue is easily reproducible. If you open a PowerShell terminal and measure the execution time of both commands, the difference is stark. You might have several network drives mapped, some of which may be slow to respond or temporarily offline.

Let’s measure it:

# Measuring the classic 'net use' command
Measure-Command { net use }

# Measuring the modern PowerShell cmdlet
Measure-Command { Get-SmbMapping }

The output often looks something like this:

net use: TotalMilliseconds: 15.7
Get-SmbMapping: TotalMilliseconds: 2104.3

A difference of over two seconds is unacceptable in performance-sensitive scripts, such as login scripts or automation that runs frequently. This isn’t just a minor inconvenience; it’s a bottleneck. So, what’s happening under the hood?

Understanding the “Why”: A Tale of Two Commands

The performance disparity isn’t a bug; it’s a result of their fundamental design and purpose. net use is a legacy utility designed for one thing: displaying basic network connection information as text, quickly. Get-SmbMapping is a modern PowerShell cmdlet that queries a richer data source to return structured objects, which inherently takes more time.

Aspect	net use	Get-SmbMapping
Origin / Architecture	Legacy MS-DOS/CMD utility. A thin wrapper around native Windows Networking APIs (NetApi32.dll).	Modern PowerShell cmdlet. Part of the PowerShell CIM/WMI infrastructure, querying the MSFT_SmbMapping class.
Output Type	Plain text. Requires string parsing for use in scripts.	Rich PowerShell Objects ([Microsoft.Management.Infrastructure.CimInstance]). Can be piped directly to other cmdlets.
Information Richness	Minimal. Provides status, local name, remote path, and network provider.	Detailed. Returns properties like `Encrypted`, `SessionId`, `ServerName`, and `ShareName` in addition to the basics.
Mechanism	Performs a quick API call to get the current session’s drive mapping table. It’s highly optimized for speed.	Initiates a WMI/CIM query. This involves more overhead as the WMI service gathers and instantiates full objects for each mapping. It may perform additional checks (like trying to resolve the remote host) that can introduce latency.

Solutions and Workarounds

Understanding the “why” is great, but we need solutions. Here are three practical approaches to solve the performance problem, catering to different needs from quick fixes to robust scripting functions.

Solution 1: Use WMI/CIM Directly

Since Get-SmbMapping is essentially a friendly wrapper for a CIM class, we can bypass the wrapper and query the underlying data source directly using Get-CimInstance. The Win32_MappedLogicalDisk class is a long-standing, highly optimized WMI provider that is often significantly faster.

This approach gives you PowerShell objects but with performance closer to that of legacy tools.

# Use Get-CimInstance to query the classic WMI class for mapped drives
Get-CimInstance -ClassName Win32_MappedLogicalDisk | Select-Object Name, ProviderName, DeviceID

# Measure the command to see the speed improvement
Measure-Command {
    Get-CimInstance -ClassName Win32_MappedLogicalDisk
}
# Typical Result: TotalMilliseconds: 50.2 (A massive improvement!)

When to use this: This is the best all-around solution. It keeps you within the PowerShell ecosystem, returns useful objects, and provides a major performance boost. It’s the ideal replacement for Get-SmbMapping in most scripts.

Solution 2: Wrap `net use` in a PowerShell Function

Sometimes, you just can’t beat the original. If you need the absolute fastest response time and are willing to do a little extra work, you can wrap the lightning-fast net use command in a PowerShell function that parses its text output into clean objects. This gives you the best of both worlds: speed and usability.

Here is a reusable function to do just that:

function Get-FastMappedDrive {
    [CmdletBinding()]
    param ()

    # Execute 'net use' and capture the output
    $netUseOutput = net use

    # Process the output line by line
    foreach ($line in ($netUseOutput -split "`r`n")) {
        # The data lines start with a status (OK, Disconnected, etc.) or a drive letter
        if ($line -match '^\s*(OK|Disconnected|Unavailable|Reconnecting)\s+([A-Z]:)') {
            # Trim leading/trailing whitespace
            $trimmedLine = $line.Trim()

            # Split the line into columns based on two or more spaces
            $columns = $trimmedLine -split '\s{2,}'

            if ($columns.Count -ge 3) {
                # Create a custom object with the parsed data
                [PSCustomObject]@{
                    Status     = $columns[0]
                    LocalPath  = $columns[1]
                    RemotePath = $columns[2]
                }
            }
        }
    }
}

# Example usage:
Get-FastMappedDrive | Where-Object { $_.Status -eq 'OK' }

When to use this: Use this approach in highly performance-critical scripts where every millisecond counts, such as startup/login scripts or rapid, repeated polling. It’s more complex to set up but offers unparalleled speed.

Solution 3: Optimize Your Use of Get-SmbMapping

While Get-SmbMapping is inherently slower, its bottleneck is the initial data retrieval. You can’t speed that part up, but you can ensure your script handles the resulting data efficiently, which can make a difference in a larger pipeline.

Instead of piping the full, rich objects through a long chain of commands, use Select-Object early to trim them down to only the properties you need. This reduces the memory footprint and processing load for subsequent cmdlets.

# Inefficient: Piping full objects
Get-SmbMapping | Where-Object { $_.Status -eq 'Unavailable' } | ForEach-Object {
    Write-Warning "The drive $($_.LocalPath) pointing to $($_.RemotePath) is unavailable."
    # ... more logic here
}

# More Efficient: Select only the needed properties early
Get-SmbMapping | Select-Object LocalPath, RemotePath, Status | Where-Object { $_.Status -eq 'Unavailable' } | ForEach-Object {
    Write-Warning "The drive $($_.LocalPath) pointing to $($_.RemotePath) is unavailable."
    # ... more logic here
}

When to use this: This is not a fix for the slow initial query. However, it’s a best practice that should be applied when you are required to use Get-SmbMapping (e.g., to get unique properties like Encrypted) and need to optimize the rest of your script around it.

Conclusion: Choosing the Right Tool for the Job

The “slowness” of Get-SmbMapping is a feature, not a bug—it’s the price of retrieving rich, structured data. However, in the world of DevOps and system administration, performance is king. You don’t always need a detailed report when a quick status check will do.

For the best balance of performance and PowerShell-native objects, switch to Get-CimInstance -ClassName Win32_MappedLogicalDisk. It should be your default choice.
For maximum speed in critical automation, take the time to build a robust parser function around the legacy net use command.
Stick with Get-SmbMapping only when you specifically need the detailed SMB information it uniquely provides, and be sure to optimize its usage in your pipeline with Select-Object.

By understanding the tools at your disposal and their underlying mechanics, you can write scripts that are not only powerful and reliable but also efficient and fast.