Archived:VxWorks Controller USB Size Limitation

Updated May 20, 2024

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Reported In


  • cRIO-9012
  • cRIO-9014
  • cFP-2220

Issue Details

Is there a size limitation on the supported USB devices for VxWorks CompactRIO (cRIO), Single-Board RIO (sbRIO), and cFP-22XX controllers? If so, what is the maximum size I can use?


VxWorks targets only support external drives of two file systems: FAT16 and FAT32. As such, the limitations on size are the same as the standard limitations for those formats. FAT16 has a 4GB limit on partition size, whereas FAT32 has a 2TB limit on partition size.


Additional Information

  • Some disks that are not initially recognized by the cRIO, sbRIO, or cFP will be recognized after reformatting the drive to meet these requirements. However, the built-in FAT32 formatting tool in Windows 2000, Windows XP, Windows Vista, and Windows 7 is limited to 32 GB. To achieve partition size above 32 GB, a third-party formatting tool may be required.
  • VxWorks does not support the extended file system (ext, ext2, ext3) nor New Technology File System (NTFS).
  • On VxWorks targets, the USB device will enumerate as the U drive by default. The drive will not show up in the root directory when connecting to the target via FTP. To access this drive via FTP, type the following address directly:
ftp://<IP Address>/u:/

The contents of the external USB drive will then appear and you can then browse through the files on the drive.
  • If you are using an external storage, which is large as 1 or 2 TB make sure that it has enough power, the device may require an external power supply.