SysGauge

SysGauge is a system and performance monitoring utility that lets you monitor CPU usage, memory usage, network throughput, operating system performance, running processes status and resource usage, file system performance, USB performance, disk space usage, disk read activity. 

disk write activity, disk read transfer rate, disk write transfer rate, disk read IOPS, and disk write IOPS for all physical disks or individual logical disks installed in the computer.