It depends if you are using Crimson 3.0 or 3.1. Crimson 3.0 is limited to FAT16 formatting which according to Wikipedia has a maximum size of 2GB or 4GB depending on the cluster size. Also you are limited on the length of the filenames. Crimson 3.1 lets you use FAT32 formatting on the drive so the limit then should in theory be about 2 terabytes. And you get longer filenames. I am using a Graphite HMI with Crimson 3.1 and can confirm that FAT32 works.