more snapshot configs

hosts/desktop/snapshot.nix

@@ -14,5 +14,18 @@
 				};
 			};
 		};
+		instances."duplicate_to_second_drive" = {
+			onCalendar = "daily";
+			settings = {
+				snapshot_preserve = "14d 8w 120m";
+				snapshot_preserve_min = "7d";
+				volume = {
+					"/media/2tb" = {
+						target = "/media/12tb/@snapshots";
+						subvolume = "@home";
+					};
+				};
+			};
+		};
 	};
 }