diff --git a/storage/src/group_commit.rs b/storage/src/group_commit.rs
index 725fd07..a83958d 100644
--- a/storage/src/group_commit.rs
+++ b/storage/src/group_commit.rs
@@ -44,7 +44,7 @@ impl Default for GroupCommitOptions {
             queue_depth: 1_024,
             max_batch_pages: 256,
             max_delay: Duration::from_micros(200),
-            checkpoint_after_wal_bytes: 64 << 20,
+            checkpoint_after_wal_bytes: 12 << 20,
             flush_pages_per_batch: 32,
         }
     }
diff --git a/storage/src/wal.rs b/storage/src/wal.rs
index 2da60c1..8f523d5 100644
--- a/storage/src/wal.rs
+++ b/storage/src/wal.rs
@@ -17,7 +17,7 @@ const NO_PAGE_ID: u64 = u64::MAX;
 /// in place, so the routine commit sync never touches file metadata.
 /// Growing a file on every append makes each sync journal a size change,
 /// which measured six times slower than syncing data blocks alone.
-const WAL_PREALLOCATE_BYTES: u64 = 64 << 20;
+const WAL_PREALLOCATE_BYTES: u64 = 16 << 20;
 /// How far ahead of the append position a segment is zero-filled.
 ///
 /// Reserving length with set_len leaves a sparse file, and writing into a