Why there is no write speed gain when using a higher RAID level?

in Part 2 – Which RAID Level should I use? we talked about the different RAID levels, now the question is, which RAID level will be the perfect one for my application?

typical RAID Levels (commonly used) provide us with these fundamental rules:

Based on a disk array based on 8 drives (see sample here)

	RAID 0	RAID 1	RAID 5	RAID 6	RAID 10
minimum disks:	2	2	3	4	4
Speed gain READ:	8x read	Up to 8x read	7x read	6x read	8x read
Sped gain WRITE:	8x write	no	no	no	4x write
use:	High End Workstation, real-time applications	OS, databases	Data warehousing, web server, archiving	High End Workstations, real-time applications, transitory data, archiving	Fast databases, application servers
Data Protection:	no protection	Single-disk failure	Single-disk failure	Two-disk failure	single disk failure in each sub-array
Capacity utilization of all disks:	100%	50%	66-94%	50-88%	50%

As we see, a write speed gain appears only when using a RAID 0, an increased write performance can be used with RAID 10 as well.

Write speed gain is a fundamental factor when handling intermediate data.

CrystalDiskMark Ramdisk to Single Drive	CrystalDiskMark Ramdisk to SSD	CrystalDiskMark Ramdisk to RAID0
CrystalDiskMark Ramdisk to Storage Pool/Storage Spaces RAID 5	CrystalDiskMark Ramdisk to JBOD	CrystalDiskMark Ramdisk to RAMDISK