Reference: Disabling disk write cache
An important note on disabling disk write cache. Warning Most disks contain hardware write caches. A write cache can increase the apparent performance of the disk because writes just go into the cache and are then lazily written to the disk later. This happens irrespective of whether you have executed a fsync() from the operating system or correctly synced data from inside a Java program! By default many systems ship with disk write cache enabled. This means that even after syncing from the operating system there is no guarantee the data has actually made it to disk, so if a failure occurs, critical data can be lost. Some more expensive disks have non volatile or battery backed write caches which won't necessarily lose data on event of failure, but you need to test them! If your disk does not have an expensive non volatile or battery backed cache and it's not part of some kind of redundant array (e.g. RAID), and you value your data integrity you need to make sure disk write cache is disabled. Be aware that disabling disk write cache can give you a nasty shock performance wise. If you've been used to using disks with write cache enabled in their default setting, unaware that your data integrity could be compromised, then disabling it will give you an idea of how fast your disk can perform when acting really reliably. On Linux you can inspect and/or change your disk's write cache settings using the tools hdparm (for IDE disks) or sdparm or sginfo (for SDSI/SATA disks) On Windows you can check / change the setting by right clicking on the disk and clicking properties.