Change IO Scheduler for your disks

More reading about the differences with different schedules. I wont copy-paste the internet here:

Benchmarks on NVME SSD - https://www.phoronix.com/scan.php?page=article&item=linux-56-nvme&num=1

Benchmarks on HDD - https://www.phoronix.com/scan.php?page=article&item=linux-50hdd-io&num=1

YMMW, you can only be sure what is best for you if you do the benchmarks yourself. How to change your schedulers and auto-apply them on every reboot?

nano /etc/udev/rules.d/60-ioschedulers.rules

Paste the code:

# set scheduler for NVMe
ACTION=="add|change", KERNEL=="nvme[0-9]*", ATTR{queue/scheduler}="none"
# set scheduler for SSD and eMMC
ACTION=="add|change", KERNEL=="sd[a-z]|mmcblk[0-9]*", ATTR{queue/rotational}=="0", ATTR{queue/scheduler}="mq-deadline"
# set scheduler for rotating disks
ACTION=="add|change", KERNEL=="sd[a-z]", ATTR{queue/rotational}=="1", ATTR{queue/scheduler}="bfq"

Apply the settings (can be done when array is started):

udevadm control --reload
udevadm trigger

You are done, the schedulers should be changed. you can verify it by typing: cat /sys/block/sdg/queue/scheduler  (sdg is your device)

mq-deadline (default for everything in UnRAID) may be better for HDD's for high throughput, all depends on your use case.