diff --git a/crates/config/src/constants/runtime.rs b/crates/config/src/constants/runtime.rs
index 783ad6993..36fc33141 100644
--- a/crates/config/src/constants/runtime.rs
+++ b/crates/config/src/constants/runtime.rs
@@ -60,9 +60,9 @@ pub const DEFAULT_RNG_SEED: Option<u64> = None; // None means random
 /// Dedicated blocking thread pool for fsync/fdatasync operations.
 /// When > 1, fsync operations are isolated from the main blocking pool to
 /// prevent device-bound fsync from starving read operations (pread/stat/open).
-/// Default 0 means auto (no isolation, use main runtime).
+/// Default 64 isolates fsync from the main blocking pool to prevent device-bound fsync from starving read I/O.
 pub const ENV_FSYNC_BLOCKING_THREADS: &str = "RUSTFS_RUNTIME_FSYNC_BLOCKING_THREADS";
-pub const DEFAULT_FSYNC_BLOCKING_THREADS: usize = 0;
+pub const DEFAULT_FSYNC_BLOCKING_THREADS: usize = 64;
 
 // Dial9 Tokio Telemetry Default values
 pub const DEFAULT_RUNTIME_DIAL9_ENABLED: bool = false; // Disabled by default