reorganization

modules/core/fs/fstrim.nix

@@ -0,0 +1,36 @@
+{ config, lib, ... }:
+
+with lib;
+{
+  # if lvm is enabled, then tell it to issue discards
+  # (this is good for SSDs and has almost no downsides on HDDs, so
+  # it's a good idea to enable it unconditionally)
+  environment.etc."lvm/lvm.conf".text = mkIf config.services.lvm.enable ''
+    devices {
+      issue_discards = 1
+    }
+  '';
+
+  # discard blocks that are not in use by the filesystem, good for SSDs
+  services.fstrim = {
+    # we may enable this unconditionally across all systems becuase it's performance
+    # impact is negligible on systems without a SSD - which means it's a no-op with
+    # almost no downsides aside from the service firing once per week
+    enable = true;
+
+    # the default value, good enough for average-load systems
+    interval = "weekly";
+  };
+
+  # tweak fstrim service to run only when on AC power
+  # and to be nice to other processes
+  # (this is a good idea for any service that runs periodically)
+  systemd.services.fstrim = {
+    unitConfig.ConditionACPower = true;
+
+    serviceConfig = {
+      Nice = 19;
+      IOSchedulingClass = "idle";
+    };
+  };
+}

modules/core/fs/lvm.nix

@@ -0,0 +1,7 @@
+{ config, lib, ... }:
+
+with lib;
+{
+  # i don't use lvm, can be disabled
+  services.lvm.enable = mkDefault false;
+}

modules/core/fs/scrub.nix

@@ -0,0 +1,16 @@
+{ config, lib, ... }:
+
+with lib;
+let
+  supportedFilesystems = builtins.map (builtins.getAttr "fsType") (builtins.attrValues config.fileSystems);
+  mkScrubConfig = fsType: {
+    enable = builtins.elem fsType supportedFilesystems;
+    interval = "weekly";
+  };
+in {
+  services.btrfs.autoScrub = mkScrubConfig "btrfs";
+  services.zfs.autoScrub = mkScrubConfig "zfs";
+
+  # bcachefs exists but it was "ejected from the kernel" for "repeated violations of kernel dev. guidelines"
+  # linus "tech tips" torvalds said himself "nobody sane uses bcachefs and expects it to be stable" (https://en.wikipedia.org/wiki/Bcachefs#Stability)
+}