Synology DiskStation Manager - DiskStation Manager is a data storage platform that comes with a completely private collaboration suite.
WinDirStat - WinDirStat is a disk usage statistics viewer and cleanup tool, inspired by KDirStat.
CTERA - CTERA is the global leader in edge-to-cloud file services.
WizTree - WizTree quickly finds the files and folders using the most space on your hard drive. It scans the MFT (Master File Table) instead of crawling the entire disk which makes it very fast.
Nutanix - Nutanix is a virtualized datacenter platform that provides disruptive datacenter infrastructure solutions for implementing enterprise-class.
SpaceSniffer - SpaceSniffer is a freeWare (donations are welcome) and portable tool application that lets you understand how folders and files are structured on your disks.