💽Make Virtual Drive for Silicon Mac

Guide for creating a virtual drive file on Apple Silicon Macs without using the Windows-only VHD Tool.

Since the Windows-based VHD Tool cannot be used directly on Apple Silicon Macs (M1, M2, M3, etc.), you can create a compatible virtual drive file using the macOS Terminal.

Recommended Resources

For more details on dummy file creation, refer to the following technical guides:

• Creating Large Dummy Files via macOS Terminal

• mkfile Command Reference (SS64)

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Step-by-Step Creation Guide

You can create a dummy file using the mkfile command. The file extension must be set to .DSK to be recognized by the IODD as a virtual drive.

Command Syntax Open the Terminal and use the following command structure: $ mkfile [Size] [Path/Filename.DSK]

Usage Examples:

• Create a 10GB Virtual Drive:

        $ mkfile 10G ~/VirtualHDD.DSK

*(Creates a 10GB virtual drive file named "VirtualHDD.DSK")*

• Create a 100GB Virtual Drive:

        $ mkfile 100G ~/ST400VD.DSK

*(Creates a 100GB virtual drive file named "ST400VD.DSK")*

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How to Prevent File Fragmentation (Critical for IODD)

The IODD hardware requires virtual drive files (DSK, ISO, VHD) to be stored in physically contiguous space (unfragmented). macOS does not have a built-in defrag utility, so follow these methods to ensure compatibility:

Method 1: Create Directly on the IODD Drive (Recommended) To prevent fragmentation from the start, execute the mkfile command directly onto the IODD drive's path.

    # Example: Creating directly on the IODD volume
    $ mkfile 20G /Volumes/Your_IODD_Name/NewDisk.DSK

Method 2: Ensure Sufficient Free Space Before creating a file, ensure the IODD has much more free space than the file size you intend to create. This allows the file system to allocate a single contiguous block of data more easily.

How to Fix "Defrag!" Errors on macOS If the IODD displays a "Defrag!" error, macOS does not provide a tool to fix this in place. You must:

1. Copy the fragmented .DSK file to your Mac's desktop.

2. Delete the file from the IODD and Empty the Trash.

3. Copy the file back to the IODD.

If the error persists, the most effective solution is to backup all data, format the IODD, and copy all files back at once.

Avoid Sparse Files Do not use the dd command with seek to create files, as this creates "sparse files" that are highly likely to be fragmented and unrecognizable by the IODD hardware. Always use mkfile.