NTFS parallel flush worker threads

When flushing modified file data from memory, NTFS chooses to use one or more threads based on how many files are currently open. This setting gives control over how many threads will be used.

Making this value larger may decrease the time it takes to flush a volume but the flush may have a larger impact on other concurrent IO operations.

Values with special meaning:
0: Use the system calculated default
1: Disable parallel flush

The default value and limit for this setting varies based on the number of available processors on a given system:
- Default value calculation is: (([NumProcessors]/2) + 1)
- Default max value calculation is: ([NumProcessors]*2)