perf(store/sync): avoid syncing files (#3693)

We don't need manual FS syncs. The underlying FS decides when to flush its internal buffers. If the FS fails to write to disk after we finish writing to it, it's a bug on the FS side. Also, during historical block sync, manually syncing files per every block to FS will apply a performance penalty for no good reason.

Also, after #3679, files become immutable, meaning we can safely do delayed writes in FS by avoiding `Sync`

store/file/ods.go

@@ -42,7 +42,6 @@ type ODS struct {
 
 // CreateODS creates a new file under given FS path and
 // writes the ODS into it out of given EDS.
-// It ensures FS is synced after writing finishes.
 // It may leave partially written file if any of the writes fail.
 func CreateODS(
 	path string,
@@ -52,7 +51,7 @@ func CreateODS(
 	mod := os.O_RDWR | os.O_CREATE | os.O_EXCL // ensure we fail if already exist
 	f, err := os.OpenFile(path, mod, filePermissions)
 	if err != nil {
-		return fmt.Errorf("creating file: %w", err)
+		return fmt.Errorf("creating ODS file: %w", err)
 	}
 
 	hdr := &headerV0{
@@ -92,10 +91,6 @@ func writeODSFile(f *os.File, axisRoots *share.AxisRoots, eds *rsmt2d.ExtendedDa
 		return fmt.Errorf("flushing ODS file: %w", err)
 	}
 
-	if err := f.Sync(); err != nil {
-		return fmt.Errorf("syncing file: %w", err)
-	}
-
 	return nil
 }
 

store/file/q4.go

@@ -28,7 +28,6 @@ type Q4 struct {
 
 // CreateQ4 creates a new file under given FS path and
 // writes the Q4 into it out of given EDS.
-// It ensures FS is synced after writing finishes.
 // It may leave partially written file if any of the writes fail.
 func CreateQ4(
 	path string,
@@ -74,10 +73,6 @@ func writeQ4File(f *os.File, eds *rsmt2d.ExtendedDataSquare, hdr *headerV0) erro
 		return fmt.Errorf("flushing Q4: %w", err)
 	}
 
-	if err := f.Sync(); err != nil {
-		return fmt.Errorf("syncing Q4 file: %w", err)
-	}
-
 	return nil
 }