nas: Garage keeps its metadata in SQLite

nas/garage/garage.toml

@@ -1,8 +1,15 @@
 # One node on the Synology. Velero's kopia data is encrypted, so
 # compression would only cost CPU.
+#
+# SQLite rather than the default LMDB: LMDB can be corrupted by an unclean
+# shutdown, and a single node has no other node to repair from. With
+# metadata_fsync SQLite runs WAL with synchronous=NORMAL, which only syncs
+# at checkpoints; LMDB with metadata_fsync synced every transaction, ~270
+# writes/s on the NAS's two disks with Garage idle. Converted 2026-10-25
+# with `garage convert-db`.
 metadata_dir = "/var/lib/garage/meta"
 data_dir = "/var/lib/garage/data"
-db_engine = "lmdb"
+db_engine = "sqlite"
 metadata_fsync = true
 data_fsync = true
 metadata_auto_snapshot_interval = "6h"