That worked perfectly. I chose a variant of the first option you suggested:
- a 4x 2TB NVME pool at L: with...
> Duplication Space Optimizer plugin enabled,
> Disk Space Equalizer plugin enabled,
> duplication enabled,
> real-time duplication disabled,
> read striping enabled
- a 1x 4TB SATA pool at M: with...
> Disk Space Equalizer plugin enabled (for when I add disks to this pool in the future),
> duplication disabled,
> read-striping enabled (for when I add disks to this pool in the future)
- a pool at N: made up of pools L: and M: with...
> the Ordered File Placement plugin enabled prioritizing the L:NVME pool for writing new files,
> duplication enabled,
> real-time duplication disabled,
> read-striping disabled (I don't want to include slow M:SATA disks in a read stripe)
With these settings:
- sequential writing to pool N: happens as fast as the max speed of one NVME disk (7000+ MBps)
- sequential reading for unduplicated files happens as fast as the max speed of one NVME disk (+/- 7000 MBps)
- sequential reading for duplicated files happens almost twice as fast as the max speed of one NVME disk (12,000+ MBps)
- my usable NVME pool capacity is 3.65TB (half of 7.3TB formatted)
- all files are hosted and duplicated on the L:NVME pool
- a 3rd copy of all files exists on the M:SATA pool
- everything can be expanded or repaired at a later date by adding or replacing disks as needed
- this all happens seamlessly through a single partition at N:
I'm particularly impressed that the M:SATA pool is intelligently only keeping 1 copy of every unique file from the L:NVME pool, and not duplicating duplicates. It just lists the duplicated files on L: as "Other".
I'm using this pool to host all my Windows User directory's libraries (Documents, Pictures, Videos, Music, etc, with the sole exception of AppData). So far, this is almost as good as ZFS in some ways, and better in other ways. It blows Intel RST, Microsoft Storage Spaces, or Windows Disk Management arrays right out of the water.
I'm annoyed I haven't discovered DrivePool sooner.