Robocopy: Reliable File Copying Utility

Robocopy (Robust File Copy) is Microsoft’s command-line directory replication tool, built into Windows since Vista/Server 2008. It replaces xcopy with superior reliability, resume capability, and advanced features for enterprise file operations.

Why Robocopy?

Essential Syntax

robocopy <Source> <Destination> [<File>[ ...]] [<Options>]

Key concept: Robocopy works with directories, not individual files. Source and destination are folder paths.

Common Use Cases

1. Basic Copy (New/Changed Files Only)

robocopy "C:\Source" "D:\Backup" /E /Z /R:3 /W:5 /LOG:copy.log

• /E - Copy subdirectories including empty
• /Z - Restartable mode (resume on interruption)
• /R:3 - Retry 3 times (default 1 million!)
• /W:5 - Wait 5 seconds between retries
• /LOG:file - Log to file

2. Mirror Directory (Exact Replica)

robocopy "C:\Source" "D:\Mirror" /MIR /Z /R:3 /W:5 /LOG:mirror.log

• /MIR = /E + /PURGE (deletes destination files not in source)
• Warning: Destination becomes exact clone, extra files deleted!

3. Incremental Backup (Daily)

robocopy "C:\Data" "\\Server\Backup\Data" /E /Z /R:2 /W:10 /XO /LOG+:daily.log

• /XO - Exclude Older (skip if destination same/newer)
• /LOG+ - Append to existing log

4. Multi-threaded High-Speed Copy

robocopy "C:\LargeFolder" "D:\Target" /E /Z /MT:16 /R:2 /W:5 /LOG:fast.log

• /MT:n - Multi-threaded (1-128 threads, default 8)
• Caution: High thread count can saturate disk/network

5. Network Copy with Throttling

robocopy "C:\Source" "\\NAS\Share" /E /Z /IPG:50 /R:5 /W:10 /LOG:netcopy.log

• /IPG:n - Inter-Packet Gap (ms) for bandwidth throttling
• Useful for WAN/VPN links

Complete Option Reference

Copy Options

File Selection

Retry & Logging

Advanced

Real-World Scenarios

Server Migration

robocopy "\\OldServer\Data" "\\NewServer\Data" /E /COPYALL /DCOPY:T /ZB /MT:16 /R:3 /W:10 /LOG:migration.log /TEE

Daily Backup to Rotating Drives

@echo off
set DEST=Z:\Backup\%DATE:~10,4%-%DATE:~4,2%-%DATE:~7,2%
robocopy "C:\Users" "%DEST%\Users" /E /Z /R:2 /W:5 /XO /LOG+:%DEST%\backup.log
robocopy "C:\Projects" "%DEST%\Projects" /E /Z /R:2 /W:5 /XO /LOG+:%DEST%\backup.log

Sync with Exclusions

robocopy "C:\Source" "D:\Sync" /MIR /XD ".git" "node_modules" "bin" "obj" /XF "*.tmp" "*.log" "Thumbs.db" /R:2 /W:5 /LOG:sync.log

Copy Only Permissions (ACLs)

robocopy "C:\Source" "D:\Dest" /E /COPY:S /IS /IT /LOG:perms.log

• /COPY:S - Security only
• /IS - Include Same (files that appear identical)
• /IT - Include Tweaked (same data, different attributes)

Exit Codes (Bitwise)

Check in batch: if %errorlevel% geq 8 echo Error occurred

PowerShell Wrapper

function Invoke-Robocopy {
    param(
        [string]$Source,
        [string]$Dest,
        [string[]]$Options = @('/E','/Z','/R:3','/W:5','/LOG+:robocopy.log')
    )
    $args = @($Source, $Dest) + $Options
    & robocopy.exe @args
    $exitCode = $LASTEXITCODE
    if ($exitCode -ge 8) {
        Write-Error "Robocopy failed with exit code $exitCode"
    }
    return $exitCode
}

Best Practices

1. Always test with /L (List only) first
2. Use /LOG for audit trails
3. Set reasonable /R and /W (not defaults)
4. Use /MT judiciously - 8-16 for local, 4-8 for network
5. Preserve timestamps with /DCOPY:T
6. Mirror carefully - /MIR deletes!
7. Test restores - Backup unverified is not a backup

Resources

• robocopy /? - Built-in help
• Microsoft Robocopy Docs
• Robocopy GUI - Community GUI wrapper
• SS64 Robocopy Reference