Maintaining the storage layer/drivers in two languages is burdensome. Since the integration tests require the Perl storage layer/drivers we'll need them even after the core code is migrated to C. Create an interface layer so the Perl code can be removed and new storage drivers/features introduced without adding Perl equivalents.
The goal is to move the integration tests to C so this interface will eventually be removed. That being the case, the interface was designed for maximum compatibility to ease the transition. The result looks a bit hacky but we'll improve it as needed until it can be retired.
This implementation should be faster because it does not stat each file. It simply assumes that most directory entries are files so attempts an unlink() first. If the entry is reported by error codes to be a directory then it attempts an rmdir().
This option allows pgBackRest to validate page checksums in data files when checksums are enabled on PostgreSQL >= 9.3. Note that this functionality requires a C library which may not initially be available in OS packages. The option will automatically be enabled when the library is present and checksums are enabled on the cluster.
