The primary function of the AXN/MXN is as a network music player and the USB port is intended for convenient connection of USB HDDs and SSDs. As such, we can not guarantee compatibility with all USB HDDs and SSDs.
There is no size limit to connected USB hard drives, however you may encounter problems if you have a very large collection on a high capacity drive. The memory included in the AXN/MXN that is required for indexing tracks from USB local Media is limited and may not be sufficient for such large collections.
The AXN/MXN will read large capacity hard drives connected to the USB Media input. Some larger capacity drives, however, may require their own power supply, as the player's USB port may not provide enough power for the drive to function.
The AXN/MXN will support USB hard drives which are formatted to FAT32, exFAT and NTFS.