The ADC-CSVR126 supports two SATA interfaces, each with 8 TB maximum storage. The maximum total storage capacity for the ADC-CSVR126 is 16 TB.
Alarm.com recommends using 3.5 inch Seagate Skyhawk or Western Digital purple series hard drives for all ADC-CSVR126 hard drive replacements. These drives have been tested and ship with the Stream Video Recorder and are specifically made for surveillance applications.
More information on the CSVR126 can be found here: