All Things PerfectDisk – and Defrag - Defrag of system files

One way PerfectDisk stands out is its ability to defragment all system files (including all NTFS metadata). System files are the designation that PerfectDisk uses to identify important files that the operating system uses at runtime to operate your PC. These include the Windows paging file (pagefile.sys), the hibernation file used to support sleep mode on desktop Windows PCs (hiberfile.sys).

Depending on whether or not the drive is a system drive, or some other drive that PerfectDisk can’t lock, offline file defragmentation may or may not run on the drive(s). As long as PerfectDisk can lock a drive for exclusive access at runtime, it will defragment system files immediately. But for a Windows system disk or any other locked drive — one, for example, where a paging file might reside in a whole or in part — attempts to defragment system files at runtime will usually fail.

These files are then defragmented if the drive is not locked. Otherwise, this occurs at boot time. PerfectDisk locks the drive for its own exclusive use, so it can then defragment and move files the operating system would otherwise not allow to be altered. So, a boot time defrag is really only mandatory for drives that cannot be locked at run time.

Occassionally when you schedule a boot time defrag pass in PerfectDisk, it doesn’t work. This is because PerfectDisk is unable to lock the drives during boot time, so the system gets booted without the defrag pass getting executed. When this happens, it is almost always because a third-party program has modified the BootExecute registry key so that PDBoot.exe (the name of the PerfectDisk boot time defragmentation executable file) is no longer the first entry in its value string. This entry must occur first in that key for boot time defrag to run correctly. Another possibility is that a third-party software product has opened the drive for write access before PDBoot.exe can mount the drive for exclusive access. If the drive is open for write access, PerfectDisk will not run a boot time/offline defrag in order to avoid potential damage to or corruption of system files.