The Ultimate Robocopy Command for Large-Scale Migrations

The Ultimate Robocopy Command for Large-Scale Migrations | Lazy Admin Blog

Posted on June 16, 2015 Updated on March 23, 2026

If you need to move huge files while keeping a close eye on progress, this is the syntax you want. It includes logging, multi-threading for speed, and the ability to resume if the network drops.

The “Power User” Command

DOS

			
robocopy "D:\Source_Data" "E:\Destination_Data" /s /e /z /mt:32 /tee /log+:"C:\Logs\MigrationLog.txt"

Switch Breakdown: Why We Use Them

Switch	What it does
/s /e	Copies all subdirectories, including empty ones.
/z	Restart Mode: If the connection drops mid-file, Robocopy can resume from where it left off instead of starting the file over. Essential for 100GB+ files!
/mt:32	Multi-Threading: Uses 32 threads to copy multiple files simultaneously. (Default is 8). Adjust based on your CPU/Disk speed.
/tee	Writes the status to the console window and the log file at the same time.
/log+:	Creates a log file. Using the `+` appends to an existing log rather than overwriting it—perfect for multi-day migrations.

How to Monitor Progress in Real-Time

Because we used the /tee and /log+ switches, you have two ways to monitor the status:

The Console: You’ll see a rolling percentage for each file directly in your Command Prompt.
Tail the Log: Since the log is being updated live, you can “tail” it from another window (or even remotely) to see the progress without touching the active copy session.

Lazy Admin Tip (PowerShell):

Open a PowerShell window and run this command to watch your Robocopy log update in real-time as files move:

Get-Content "C:\Logs\MigrationLog.txt" -Wait

Important Notes for Huge Files

Disk Quotas: Robocopy doesn’t check destination space before starting. Use dir or df (if using Linux targets) to ensure you have enough room.
Permissions: If you need to copy NTFS permissions (ACLs), add the /copyall switch.
Bandwidth: Running /mt:128 (the max) can saturate a 1Gbps link. If you’re copying over a live production network, stick to /mt:8 or /mt:16.