Based on the RAID technology in the following scenarios, identify the best RAID Level (0 to 6) that should be used:

1. Network File System which require high reliability but with moderate complexity, by distributing the data and parity strips evenly across all disks in the array.
2. Media streaming for High Definition Video, where extremely high throughput is required.
3. E-Commerce Transaction database requiring very high reliability where data recovery is possible even with two disk failures.
4. Real Time Medical Diagnostics system requiring high reliability and high throughput.