I’m not aware of Syncthing having those two features/options, but there are ways to do what you’re looking for…
The index database is pretty crucial to Syncthing’s functionality so there are caveats to holding it in RAM. If your NAS has very reliable power and/or is backed by an UPS, then relocating the database to a ramdrive or similar volatile storage is one option. You’d also need to back up and restore the database whenever the NAS is rebooted otherwise it’d be almost like a
If your NAS unit has a USB port, a less complicated alternative is to relocate the database to a USB flash drive or SSD (the latter is best given the much higher TBW).
Or if you’re not constantly updating your music collection, perhaps use Syncthing’s API to pause the remote device connection to your RPi whenever there has been no changes for some preset number of hours.
There’s reducing power consumption to save money on electricity, and then there’s doing it to save the environment. Neither is mutually exclusive and both are worthwhile.
As a sysadmin maintaining servers in data centers, I’ve seen first hand how putting HDDs to sleep saves electricity, which in turn reduces the load on power (e.g., UPS, generators, etc.) and cooling systems. It all adds up to significant savings when multiple 42U server racks are involved (a single rack can easily require more than 4KW of power).
However, spinning up the motor in a HDD causes extra wear. An earlier study on HDD longevity found that each time a HDD is spun up is equivalent to about 6 hours of wear. Or in other words, spinning up a HDD once every 4 hours during the course of a day is the same as if the HDD had been spinning continuously for 24 hours.
According to Western Digital, a 6TB “Red Plus” (WD60EFZX) has the following power profile:
Standby and sleep 0.4
Assuming an electricity rate of $0.11/kWh, the difference between idle and standby/sleep is $3.57 per year (can be lower or significantly higher elsewhere). A shortened lifespan can easily cost more than the electricity saved – a WD60EFZX is around $106, so the break even point is as much as 29 years.
It takes a tremendous amount of electricity to produce aluminum (HDD platters are nearly 100% aluminum; enclosures are more than 75% by volume). The semiconductors, CNC machines, polishers, lasers, electronic waste, etc. add to the total environmental impact, so keeping a HDD in service for as long as possible is ideal.