Robocopy (Robust File Copy) is one of Microsoft's most powerful command-line utilities for copying, synchronizing, and backing up files and folders. Built into modern versions of Windows, Robocopy is designed to handle large datasets, network interruptions, file permissions, and complex directory structures more efficiently than traditional copy methods.

A commonly used Robocopy command for creating a safe copy of one drive to another is:

robocopy D:\ E:\ /E /COPY:DAT /DCOPY:DAT /MT:32 /R:0 /W:0 /XJ /FFT /TEE /V /LOG:E:\CopyDToE.log

Unlike mirror operations, this command safely copies files without deleting anything already present in the destination drive. It is ideal for backups, drive migration, external storage, and disaster recovery preparations.

Understanding the Command

Source Drive

D:\

This is the source drive containing the files and folders to be copied.

Destination Drive

E:\

All copied files are written to the destination drive.

Existing files remain untouched unless the source contains a newer version.

Detailed Breakdown of Every Switch

/E

Copies:

• All directories
• All subdirectories
• Empty folders

Without this switch, empty directories would not be copied.

/COPY

Copies only:

• File Data
• File Attributes
• File Timestamps

It intentionally does not copy:

• NTFS Security Permissions (ACL)
• File Ownership
• Auditing Information

This makes the command safer when copying to drives with different security requirements.

/DCOPY

Copies folder:

• Attributes
• Timestamps

Folder permissions remain unchanged.

/MT:32

Enables multi-threaded copying using 32 simultaneous threads.

Benefits

• Much faster copy performance
• Excellent SSD utilization
• Better CPU utilization
• Faster processing of thousands of files

Recommended Values

Storage Type	Suggested Threads
HDD	8-16
SATA SSD	16-32
NVMe SSD	32-64
Network Share	16-32

/R:0

Retry count is zero.

If a file is locked or inaccessible, Robocopy skips it immediately instead of waiting.

Ideal for servers where Outlook PST files, databases, or browser cache files may be in use.

/W:0

Wait time between retries is zero seconds.

Since retries are disabled, the command continues immediately.

/XJ

Excludes NTFS Junction Points.

This prevents:

• Infinite recursion
• Duplicate copies
• Circular directory structures

Especially useful when copying Windows user profiles.

/FFT

Uses FAT File Time tolerance.

Robocopy allows a two-second timestamp difference before deciding that a file has changed.

Benefits include:

• Reduced unnecessary copying
• Better compatibility with NAS devices
• Better compatibility with USB drives
• Better compatibility between different file systems

/TEE

Displays output on screen while simultaneously writing it to the log file.

Useful for monitoring long copy operations.

/V

Verbose mode.

Every processed file is displayed.

Provides detailed information useful for troubleshooting.

/LOG:E:\CopyDToE.log

Creates a comprehensive log file containing:

• Start time
• End time
• Files copied
• Files skipped
• Errors encountered
• Summary statistics

Logs are invaluable for auditing and troubleshooting.

What This Command Does

This command will:

✔ Copy all folders

✔ Copy all files

✔ Copy empty folders

✔ Preserve timestamps

✔ Preserve file attributes

✔ Preserve folder timestamps

✔ Skip identical files

✔ Copy only changed files

✔ Skip locked files immediately

✔ Use 32 simultaneous threads

✔ Display progress

✔ Generate a detailed log file

What This Command Does NOT Do

It does not:

❌ Delete destination files

❌ Mirror the source

❌ Remove extra files from destination

❌ Copy NTFS permissions

❌ Copy ownership

❌ Copy auditing information

❌ Copy Junction Points

Difference Between This Command and /MIR

Current Command

Destination only grows.

Deleted source files remain safely stored in the backup.

Perfect for:

• Backup
• Archive
• Drive migration
• External hard disks

/MIR Command

Mirror mode deletes files that no longer exist in the source.

Destination becomes an exact copy.

Ideal only for synchronization when both locations must remain identical.

Example Scenario

Suppose:

Source

D:\Photos\

contains

Vacation.jpg
Family.jpg

Destination

E:\Photos\

already contains

Vacation.jpg
Family.jpg
OldPicture.jpg

After running the command:

Vacation.jpg
Family.jpg
OldPicture.jpg

All remain.

Nothing is deleted.

Handling Existing Files

If a destination file is:

• Identical → Skipped
• Older → Replaced
• Missing → Copied

Only changed files consume copy time.

Handling Locked Files

If Outlook, SQL Server, Chrome, or another application locks a file:

Robocopy reports an error and skips the file immediately.

The remainder of the copy continues uninterrupted.

Performance Benefits

Compared to Windows Explorer, Robocopy offers:

• Better reliability
• Faster performance
• Multi-threading
• Resume capability
• Detailed logging
• Better error handling
• Lower failure rate on large datasets

Best Use Cases

This command is ideal for:

• External hard drive backups
• SSD migration
• HDD replacement
• File server backups
• Daily incremental backups
• Large multimedia collections
• Office document archives
• NAS data transfers

Safety Considerations

Because this command never deletes destination files, it is considered one of the safest Robocopy configurations.

It minimizes the risk of accidental data loss while efficiently updating the backup with new and modified files.

Advantages

• Safe operation
• Fast multi-threaded copying
• Detailed logging
• Preserves timestamps
• No destination deletion
• Skips locked files
• Supports huge datasets
• Excellent for incremental backups

Limitations

• Does not preserve NTFS permissions
• Does not delete obsolete destination files
• Locked files are skipped
• Cannot copy open databases without Volume Shadow Copy

Recommended Enhancements

For production environments, consider adding:

/Z

Restartable mode.

/NP

Suppress percentage progress for smaller log files.

/ETA

Display estimated completion time.

/LOG+

Append to an existing log instead of overwriting it.

Conclusion

The command:

robocopy D:\ E:\ /E /COPY:DAT /DCOPY:DAT /MT:32 /R:0 /W:0 /XJ /FFT /TEE /V /LOG:E:\CopyDToE.log

is an excellent choice for safely copying files from one drive to another while preserving timestamps and attributes. Since it never deletes existing files from the destination, it provides an extra layer of protection against accidental data loss, making it suitable for backups, migrations, and routine file maintenance. With multi-threaded performance, detailed logging, and robust error handling, Robocopy remains one of the most reliable file copy tools available in Windows.

 

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