> [!BaseBackupSync] > <table><tr><td rowspan="4" width="25%"><img src="assets/wl_io_basebackupsync.png"></td><td><b>Wait Category</b></td><td>IO</td></tr><tr><td><b>Mechanism</b></td><td><code>pg_basebackup</code></td></tr><tr><td><b>Operations</b></td><td><a href="Operations/ResultSet/Materialize">Materialize</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"><b>Data Durability Milestone</b>. During a physical backup, Postgres must ensure that the copied data is not just sitting in the OS page cache, but has actually reached the physical media to guarantee a recoverable state.</td></tr></table>