How Reliance Works
Datalight Relianceâ„¢ is a two state file system, the Working State and the Committed State. Original data (the Committed State) is preserved until the new data (the Working State) is written and a transaction point is performed. During operation on the Working State, all file system modifications - including changes to directories, files and metadata - are stored on an area of the media that is currently unused and does not contain Committed State data. The possibility of corruption is eliminated because the data of the new transaction is written to an unused portion of the media. Writing to an unused portion of the media allows the previous state of the file system to be untouched. Valid data from the previous transaction is always available.
Transaction Points
A significant event in the operation of the Reliance file system is the setting of a transaction point. When one or more file operations are successfully completed and data is committed to the storage media, a transaction point is set by the file system. It is at that moment that the file system changes from the previous Committed State to the new Committed State. The transaction point defines the state of the file system at the completion of one or more file I/O operations and remains the valid transaction point until the next transaction point is established.
How Reliance Preserves Data
The following illustration shows the basic concept employed by Reliance and how a transaction point is set. Reliance keeps track of unused (or free) data blocks on the storage media and always writes data to these blocks, thereby preserving all existing valid and committed (to storage) file data. Under no circumstances does Reliance overwrite existing data blocks. In this manner, the previous state of the file system remains intact on the storage media during the current write operation.
Additional documents providing more technical details are available in Resources