Editing Data remanence (section)

=== Advanced storage systems ===
Data storage systems with more sophisticated features may make [[#Overwriting|overwrite]] ineffective, especially on a per-file basis. For example, [[journaling file system]]s increase the integrity of data by recording write operations in multiple locations, and applying [[Transaction processing|transaction]]-like semantics; on such systems, data remnants may exist in locations "outside" the nominal file storage location. Some file systems also implement [[copy-on-write]] or built-in [[revision control]], with the intent that writing to a file never overwrites data in-place. Furthermore, technologies such as [[RAID]] and [[File system fragmentation|anti-fragmentation]] techniques may result in file data being written to multiple locations, either by design (for [[Fault-tolerant design|fault tolerance]]), or as data remnants.

[[Wear leveling]] can also defeat data erasure, by relocating blocks between the time when they are originally written and the time when they are overwritten. For this reason, some security protocols tailored to operating systems or other software featuring automatic wear leveling recommend conducting a free-space wipe of a given drive and then copying many small, easily identifiable "junk" files or files containing other nonsensitive data to fill as much of that drive as possible, leaving only the amount of free space necessary for satisfactory operation of system hardware and software. As storage and system demands grow, the "junk data" files can be deleted as necessary to free up space; even if the deletion of "junk data" files is not secure, their initial nonsensitivity reduces to near zero the consequences of recovery of data remanent from them.{{Citation needed|date=August 2014}}