In a RAID 6 array with four disks, what is the total usable data storage...

RAID 6 Array: RAID 6 uses double parity for data protection, which means two disks' worth of capacity is used for parity information.

Capacity Calculation: In a RAID 6 array with four disks, each 200 GB, the usable data storage capacity is calculated as follows:Total Disk Capacity=4×200 GB=800 GBTotal Disk Capacity=4×200 GB=800 GBUsable Capacity=Total Disk Capacity−Parity Disk Capacity=800 GB−2×200 GB=400 GBUsable Capacity=Total Disk Capacity−Parity Disk Capacity=800 GB−2×200 GB=400 GB

References: Dell ISM V5 Course, Module on RAID Configurations and Data Protection.