[NixOS] Set Up Zram Swap

zram-nixos.md

Zram nixos

zramSwap in NixOS enables compressed swap space in RAM using the kernel's zram module, acting as a faster, disk-free alternative to traditional swap partitions or files. It's ideal for systems with sufficient RAM and helps reduce SSD wear.

• Enable zramSwap in your configuration with:

  boot.kernelModules = [ "zram" ];
  zramSwap = {
    enable = true;
    priority = 100; # Higher than disk swap to prefer zram
    algorithm = "zstd"; # Balances speed and compression
    memoryPercent = 50; # Use up to 50% of RAM for zram
  };

• Key benefits: Faster than disk swap, no disk I/O, reduces SSD wear.

• Trade-offs: Uses CPU for compression; not suitable for hibernation (requires a swap partition equal to RAM size).

• Advanced use: Supports writeback to a disk device for incompressible data via writebackDevice.

For detailed options, see the NixOS Wiki or the zram.nix module source.