How does Double-Take® asynchronous replication technology ensure that data integrity is maintained, particularly with intra-dependent files like SQL and Oracle?
How Applications Write Data to Disk
All applications write data to persistent storage media such as a disk drive in three basic steps: Open/Create a file, Add/Update data to the file, and Close the file. Modern operating systems provide multiple software layers that provide assistance to the application write process to ensure that the file maintains a consistent state that the application can recognize the next time that it reads the file. The operating system kernel provides a set of basic functions (API) that an application can use to read and write data to disk. This reduces the complexity by providing a single interface rather than a unique method for each possible type of application data or underlying media. The API provides transparency, allowing applications to write to disk, tape, flash memory devices, etc. Most desktop applications store all of their data in memory and write an entire file to disk, relying on the file system to perform journal write protection to preserve data state. However, database applications must provide their own recovery features to preserve state.