If you read the manual the answers are there, 44.1Mhz on everything.
Use 7200 RPM and up spinning Disks. Raid 5 Enclosure with 3 drives can give you 1500 RPM connected to a laptop.
USB Hard Drives
A USB hard drive stores data on spinning magnetic disks. This is the recommended type of USB media to use with the uTrack-X32, because it has reliable and constant read/write speeds.
USB Flash Memory Devices
A USB Flash Memory Device uses flash memory. Small, cheap flash devices are generally not adequate for use with the uTrack-X32, since they require occasional pauses in data writing. This is problematic for a device that needs to write a constant data stream: a pause in data writing may cause dropouts in your recording.
Some flash devices will perform correctly. Generally, it is easier to find a usable flash device within the ones marketed as SSDs (Solid-state Drives).