The use of partitioning of HDD’s (Hard Disk Drives) is a hold-over from decades ago, when the OS’s could not see large HDD’s. This is now not a problem, up to 2TB.
Partitioning basically tells the OS that one has more physical HDD’s, than are actually available. The OS will now call for read/writes simultaneously, not realizing that it’s dealing with only one physical HDD. One of the first laws of physics is that an object cannot be in two places at the same time. In this case, it is the heads over different places on the platters at the same time. The OS expects this, and gets very confused, when there is a big hold up.
Partitions slow down the transfer of data and by a very large amount. They also cause much more wear and tear on a HDD, leading to premature failure. Because the data is spread much more with partitions, than if it had been written to a defragmented single HDD, even just the process of moving the heads is amplified - they must now travel over much larger distances, than without the partitions. This also leads to increased heat production, affecting everything in the case.
Especially with video editing, one wants to spread out the HDD workload (the work of the I/O subsystem) as much as is possible, and this spread needs to be over physical HDD’s and not logical HDD’s. That is why having more than one physical (very important) HDD is highly recommended. Two physical HDD’s is a start, three is better, and four would be excellent. This allows one to spread the workload over multiple HDD’s, increasing usable throughput.
The only reasons in this day and age, to use partitions, would be for system backup, or dual-boot setups. In the first, one would have a tiny partition holding an image of the OS, but this would not be accessed during normal work. The same would be for a dual-boot system, as one would have the programs installed on each partition for their respective OS’s. Both partitions would not be accessed at the same time.
Partitions are best done away with, especially if one wishes to have good I/O performance, longer HDD life, and a cooler case.