> [!WALSync] > <table><tr><td rowspan="4" width="25%"><img src="assets/wl_io_walsync.png"></td><td><b>Wait Category</b></td><td>IO</td></tr><tr><td><b>Mechanism</b></td><td><code>XLogWrite</code></td></tr><tr><td><b>Operations</b></td><td><a href="Operations/Tuple/ModifyTable">ModifyTable</a>, <a href="Operations/Distributed/Redistribute">Redistribute</a></td></tr><tr><td><b>Resources</b></td><td><a href="Resources/disk IO">disk IO</a>, <a href="Resources/CPU">CPU</a></td></tr><tr><td colspan="3">This wait event is the definitive measure of <b>Storage Durability Latency</b>. While <code>WalWrite</code> measures the time to hand data to the kernel, <code>WalSync</code> measures the time it takes for the kernel to execute an <code>fsync()</code> or <code>fdatasync()</code> and receive a hardware acknowledgment that the bytes are on non-volatile media.</td></tr></table>