zfs: tweak settings

modules/zfs.nix

@@ -24,31 +24,8 @@ in
   boot.initrd.kernelModules = [ "zfs" ];
 
   boot.kernelParams = [
-    # 120s TXG timeout: batch more dirty data per transaction group so the
-    # HDD pool (hdds) writes larger, sequential I/Os instead of many small syncs.
-    # This is a global setting (no per-pool control); the SSD pool (tank) syncs
-    # infrequently but handles it fine since SSDs don't suffer from seek overhead.
-    "zfs.zfs_txg_timeout=60"
-
-    # Cap ARC to prevent it from claiming memory reserved for hugepages.
-    # Without this, ZFS auto-sizes c_max to ~62 GiB on a 64 GiB system,
-    # ignoring the 11.5 GiB of hugepage reservations.
+    "zfs.zfs_txg_timeout=30"
     "zfs.zfs_arc_max=${toString arcMaxBytes}"
-
-    # vdev I/O scheduler: feed more concurrent reads to the block scheduler so
-    # mq-deadline has a larger pool of requests to sort and merge into elevator sweeps.
-    # Default async_read_max is 3 — far too few for effective coalescence.
-    # 32 was empirically optimal (64 overwhelmed the drives, 3 gave near-zero merges).
-    "zfs.zfs_vdev_async_read_max_active=16"
-    "zfs.zfs_vdev_async_read_min_active=4"
-
-    # Merge reads within 128 KiB of each other (default 32 KiB). On HDDs, reading a
-    # 128 KiB gap is far cheaper than a mechanical seek (~8 ms).
-    "zfs.zfs_vdev_read_gap_limit=131072"
-
-    # Allow ZFS to aggregate I/Os up to 4 MiB (default 1 MiB), matching the
-    # libtorrent piece extent size for larger sequential disk operations.
-    "zfs.zfs_vdev_aggregation_limit=4194304"
   ];
 
   boot.supportedFilesystems = [ "zfs" ];