#!/usr/bin/env bash

# This has not been tested, use at your own risk.

# Changes recommended for reducing writes on SSDs, this is generally all bad for hard drives: https://serverfault.com/questions/950794/how-to-limit-zfs-writes-on-nvme-ssd-in-raid1-to-avoid-rapid-disk-wear/950896#950896

# This may cause data loss and increase other resource usage (like CPU, etc).

# This script assumes your zfs pool is rpool.

echo "Enabling a variety of settings to reduce writes on SSDs. This may cause data loss and increase the usage of other resources like CPU. DO NOT run this on a hard drive. Hit Ctrl + C to cancel."

sleep 10

echo 'options zfs zfs_txg_timeout=30' > /etc/modprobe.d/zfs.conf # Set txg_timeout to 30 seconds. This introduces a higher risk of data loss.
zfs set atime=off rpool # Turn off atime.
zfs set logbias=throughput rpool # Change logbias to throughput.
zfs set compression=lz4 rpool # Set compression to lz4 instead of the older LZJB.
zfs set recordsize=16K rpool # This works better with lots of little writes, and seems to be recommended for VMs on SSDs unless your workload is many large writes.

# ZFS seems to recommend smaller recordsizes for VMs if you're running on SSDs in general depending on the workload:
# https://openzfs.github.io/openzfs-docs/Performance%20and%20Tuning/Workload%20Tuning.html#virtual-machines
# https://openzfs.github.io/openzfs-docs/Performance%20and%20Tuning/Workload%20Tuning.html#zvol-volblocksize
# 16K: https://serverfault.com/a/1120640

echo "This is the ashift, this should be 12:"
zpool get all | grep ashift

echo "And trim should be enabled:"
systemctl status fstrim.timer