This is a question we receive often, so here is the answer.
First how does it work?
Drive Bender's file duplication process is actually quite straight forward. Drive Bender stores all duplicate files in a sub folder that is a child folder of the primary file's location. This sub folder is called "FOLDER.DUPLICATE.$DRIVEBENDER". When Drive Bender creates a new file within the pool, it checks for the existence of this duplication sub folder, and if it does exist, it then creates a second file of the same name in this folder. All subsequent writes to this file and also written to the duplicate. This also applies to other files system operation such as attribute changes, file name changes etc. The one key point to make here is that Drive Bender will ensure that the primary and duplicate files sit on different physically hard drives.
With regards to performance, these write operations are threaded to ensure paralleled execution. As a result the time takes to perform a write request is determined by the slowest targeted drive.
Is it safe?
Drive Bender goes to great lengths to ensure duplicate files are valid and safe. First of all when a user enabled duplication of a folder, the duplication sub folder is created and a duplication task (also known as a validation task) is assigned to that folder. This validation task scans the folder checking the duplicate files against their primary counter parts, if there is an issue, i.e. the duplicate does not exist, or does not match the primary file, the file is duplicated. This task is also persisted across reboots to ensure that a power outage or some other event does not prevent the folder from being duplicated.
The next level of safety is the "Health Monitor". This is a threaded operation that scans the entire file system looking for files that are either not duplicated, or do not match the primary file. If any are detected, they are scheduled for validation to ensure they are consistent. This process occurs every 1 to 4 days depending on the version of Drive Bender you are running, so even if a file has not been duplicated correctly, it will be found and fixed during the next health monitor scan.