Is there any performance difference on high-disk usage scenarios, between primary and extended disk partitions?
Partitions don't really exist for the harddrive. They are just some structure the os uses. The os needs them to have different filesystems on one hd. The information that a partition consists of is basically startpos length. This information is cached by the os and given to its block device layer. When accessing the disk the starting offset of the partition is added to the block the filesystems wants to write to. Thats it.
Extended partitions have a small disadvantage during initialization. There is an additional reference that needs to be resolved which might cause one more io request. This should not be any problem.
No, you will have zero performance difference between a primary and extended partition if that is the only difference.
However, if the partitions are at different locations on disk, you will notice a difference for that reason.
Not that I would know of, it depends more on the speed of the disk, disk caching, and your usage of the disk. It depends on what you're doing. Video editing? Database access? Do you have heavily accessed data on different drives from the OS, and on a different channel?
If you're just partitioning things on one drive it's not going to help or matter much if it's a extended or primary disk. You're going to be physically limited by the I/O throughput the disk can manage to push.
There are no appreciable difference in terms of performances. Primary partitions should be used whenever you have to not worry about old OS's idiosyncrasies.
I usually use forced primary partitions for swap and /boot, just for clearness