Most hard disk controllers and hard disks are rated in terms of data throughput, usually expressed in the number of MegaBytes (MB, or 1024x1024=1048576 bytes) that can be transferred per second. These ratings can be confusing since there is Peak, Sustained, and Average throughput to consider, as well as how the reads/writes are performed (buffered, unbuffered, sequential, random, etc.). Let's avoid these details for a moment and consider how much theoretical disk I/O bandwidth is required for a large Pro Tools sessionDoing the math, 64 tracks of 24-bit, 48 kHz audio data represents approximately 8.8 MB/sec, the maximum for a Pro Tools TDM session (64 tracks x 3 bytes per sample x 48000 samples per second = 8.8 MB/sec). Pro Tools LE supports 24 tracks, so the maximum LE throughput requirement is approximately 3.3 MB/sec. Pro Tools FREE supports 8 tracks, yielding a maximum of 1.1 MB/sec.