servo: replace zfs pool with a btrfs pool

hosts/by-name/servo/fs.nix

@@ -1,60 +1,9 @@
-# zfs docs:
-# - <https://nixos.wiki/wiki/ZFS>
-# - <repo:nixos/nixpkgs:nixos/modules/tasks/filesystems/zfs.nix>
-#
-# zfs check health: `zpool status`
-#
-# zfs pool creation (requires `boot.supportedFilesystems = [ "zfs" ];`
-# - 1. identify disk IDs: `ls -l /dev/disk/by-id`
-# - 2. pool these disks: `zpool create -f -m legacy pool raidz ata-ST4000VN008-2DR166_WDH0VB45 ata-ST4000VN008-2DR166_WDH17616 ata-ST4000VN008-2DR166_WDH0VC8Q ata-ST4000VN008-2DR166_WDH17680`
-#   - legacy documented: <https://superuser.com/questions/790036/what-is-a-zfs-legacy-mount-point>
-# - 3. enable acl support: `zfs set acltype=posixacl pool`
-#
-# import pools: `zpool import pool`
-# show zfs datasets: `zfs list` (will be empty if haven't imported)
-# show zfs properties (e.g. compression): `zfs get all pool`
-# set zfs properties: `zfs set compression=on pool`
 { lib, pkgs, ... }:
 
 {
   # hostId: not used for anything except zfs guardrail?
   #   [hex(ord(x)) for x in 'serv']
   networking.hostId = "73657276";
-  boot.supportedFilesystems = [ "zfs" ];
-  # boot.zfs.enabled = true;
-  boot.zfs.forceImportRoot = false;
-  # scrub all zfs pools weekly:
-  services.zfs.autoScrub.enable = true;
-  boot.extraModprobeConfig = ''
-    ### zfs_arc_max tunable:
-    # ZFS likes to use half the ram for its own cache and let the kernel push everything else to swap.
-    # so, reduce its cache size
-    # see: <https://askubuntu.com/a/1290387>
-    # see: <https://serverfault.com/a/1119083>
-    # see: <https://openzfs.github.io/openzfs-docs/Performance%20and%20Tuning/Module%20Parameters.html#zfs-arc-max>
-    # for all tunables, see: `man 4 zfs`
-    # to update these parameters without rebooting:
-    # - `echo '4294967296' | sane-sudo-redirect /sys/module/zfs/parameters/zfs_arc_max`
-    ### zfs_bclone_enabled tunable
-    # this allows `cp --reflink=always FOO BAR` to work. i.e. shallow copies.
-    # it's unstable as of 2.2.3. led to *actual* corruption in 2.2.1, but hopefully better by now.
-    # - <https://github.com/openzfs/zfs/issues/405>
-    # note that `du -h` won't *always* show the reduced size for reflink'd files (?).
-    # `zpool get all | grep clone` seems to be the way to *actually* see how much data is being deduped
-    options zfs zfs_arc_max=4294967296 zfs_bclone_enabled=1
-  '';
-  # to be able to mount the pool like this, make sure to tell zfs to NOT manage it itself.
-  # otherwise local-fs.target will FAIL and you will be dropped into a rescue shell.
-  # - `zfs set mountpoint=legacy pool`
-  # if done correctly, the pool can be mounted before this `fileSystems` entry is created:
-  # - `sudo mount -t zfs pool /mnt/persist/pool`
-  fileSystems."/mnt/pool" = {
-    device = "pool";
-    fsType = "zfs";
-    options = [ "acl" ];  #< not sure if this `acl` flag is actually necessary. it mounts without it.
-  };
-  # services.zfs.zed = ... # TODO: zfs can send me emails when disks fail
-  sane.programs.sysadminUtils.suggestedPrograms = [ "zfs-tools" ];
 
   sane.persist.stores."ext" = {
     origin = "/mnt/pool/persist";
@@ -80,16 +29,18 @@
     fsType = "vfat";
   };
 
-  # slow, external storage (for archiving, etc)
-  fileSystems."/mnt/usb-hdd" = {
-    device = "/dev/disk/by-uuid/aa272cff-0fcc-498e-a4cb-0d95fb60631b";
+  fileSystems."/mnt/pool" = {
+    device = "/dev/disk/by-partuuid/14a7d00a-be53-2b4e-96f9-7e2c964674ec";
     fsType = "btrfs";
     options = [
-      "compress=zstd"
+      # "compress=zstd"  #< not much point in compressing... mostly videos and music; media.
       "defaults"
+      # "device=/dev/disk/by-partuuid/14a7d00a-be53-2b4e-96f9-7e2c964674ec"
+      "device=/dev/disk/by-partuuid/6b86cc10-c3cc-ec4d-b20d-b6688f0959a6"
+      "device=/dev/disk/by-partuuid/7fd85cac-b6f3-8248-af4e-68e703d11020"
+      "device=/dev/disk/by-partuuid/ef0e5c7b-fccf-f444-bac4-534424326159"
     ];
   };
-  sane.fs."/mnt/usb-hdd".mount = {};
 
   # FIRST TIME SETUP FOR MEDIA DIRECTORY:
   # - set the group stick bit: `sudo find /var/media -type d -exec chmod g+s {} +`