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PerfectDisk Logo.png
Developer(s) Raxco Software
Stable release 14 (July 22, 2015 (2015-07-22)) [±]
Operating system Microsoft Windows
Type Defragmentation utilities
License Proprietary
Website Raxco Official Website

PerfectDisk is the name of separate but related defragmentation utilities for Windows and HP OpenVMS published by Raxco Software. It has won several awards from computer magazines,[1] and is certified by Microsoft for all its current NTFS-based operating systems.[2] The current version is PerfectDisk 14.0.

PerfectDisk has editions designed for most user categories, from home PCs to large servers and virtualization-aware editions for virtual environments. In addition to defragmenting files, it also optimizes disk drives with an optimization strategy called SMARTPlacement[3] and it prevents fragmentation with the OptiWrite feature. PerfectDisk defragments data and system files and places a high priority on free space consolidation. SSD Optimize is an optimization method for solid state drives that focuses on free space consolidation without defragmentation of files.

The OpenVMS version of PerfectDisk, still in production, predated the Windows version by several years and contributed much of the approach adopted by the Windows versions. It was developed by William Davy and operates on the Files-11 file system used by OpenVMS. It features a single-pass, four-phase algorithm, intelligent placement (moving infrequently-accessed data to the periphery of the disk to reduce average seek distance,) locating directory files near indexf.sys (the Files-11 counterpart to the FAT or MFT) and clustering of "volatile" files, which attempts to make a file deletion more likely to occur adjacent to existing free space. It was the first defragmenter capable of defragmenting an open file that was actively being written, by combining the defragmenter with specialized functionality of Raxco's Data Caching product, PerfectCache, forming a product called UltraDisk.

In the mid-1990s, Raxco assigned several developers to create a Windows version of the defragmenter. Since the original product was written in VAX Macro (assembly language), starting from the existing source code was not a viable solution. Instead, the defragmentation strategy, which was largely applicable to Windows file systems despite coming from a different operating system, was refined and applied to a new code base.

Raxco released PD Free, PerfectDisk Free Defrag, in late March 2012 as an exclusive download at CNET PD Free is a fully functional free defrag utility using PerfectDisk's patented features including SMARTPlacement, SSD Optimize, Boot Time Defrag and Quick Defrag as well as scheduling options. As of April 2, 2012, PD Free is available as a free software download on most major download websites.


The OptiWrite fragmentation prevention feature detects when Windows is going to fragment files and intelligently redirects I/O to stop the fragmentation from occurring.

PerfectDisk defragmentation/optimization methods:

  • SMARTPlacement is PerfectDisk's patented default method that defragments all files, consolidates free space, and optimizes the drive according to file usage. It provides the most complete defragmentation possible and slows down refragmentation of the drive.
  • Defrag Only defragments only fragmented files without attempting to place files according to usage patterns or attempting to consolidate free space. It provides the fastest defragmentation pass of all PerfectDisk methods but is not the most thorough and it should only be used if you have lots of free space.
  • Consolidate Free Space defragments all files and consolidates free space which explains why this method sometimes takes longer to complete. Free space consolidation is best for shrinking or growing disk partitions, when seeking to re-size virtual machines, or to provide a boost to lagging Windows performance when PerfectDisk itself recommends running this defragmentation method.
  • Prep for Shrink is specifically designed to pack all data to the beginning of a volume and may result in the creation of file fragmentation. The primary purpose is to prep a partition or volume for the best possible resize or shrink. As such, it should not be used unless it is the user's intent to resize or shrink a volume or partition.
  • SSD Optimize consolidates free space on a Solid State Drive to improve SSD write performance. SSDs are not affected by file fragmentation like traditional electromechanical disk drives and defragmentation can shorten the lifespan of the SSD. SSD Optimize improves SSD performance without unnecessarily and harmfully defragmenting the drive.

PerfectDisk attempts to defragment drives in a single pass of a drive, as opposed to a common approach of running continuously and gradually defragmenting the file system.[4]

PerfectDisk has the capability of a scheduled defrag managed by an internal task scheduler.[5] It also offers the option to defrag during screen saver activity, or when the PC is idle.

In 2007 it was the first utility to support defragmentation of terabyte-sized drives. Enterprise features include integration with Active Directory, enterprise-wide defrag management and reporting. More recently the product has added support for defragmentation of virtual environment files and images.[6]

The Boot-time defrag facility is capable of defragmenting Windows meta data,[7] Master File Table, hibernation file and page file. It was the first utility to offer Free Space defragmentation, and the SMARTPlacement algorithm places older (program) files near start of the drive, and newer (data) files near the end of the drive, closer to free space in order to minimize refragmentation.[8] This optimization strategy aims to organize files by usage, resulting in a slower rate of refragmentation and also fewer resources being consumed.


The PerfectDisk product range is segmented into the following editions:

For Home

  • PerfectDisk Free Defrag is a fully functional free defrag that optimizes desktops and laptops with Quick Defrag and defaults to the SMARTPlacement intelligent optimization strategy. Boot Time Defrag is available as is SSD Optimize.
  • PerfectDisk 13.0 Pro for workstations, laptops and standalone PCs running Windows 8, Windows 7, Windows Vista, and Windows XP provides flexibility, control, and automation with its patented advanced SMARTPlacement optimization technology, OptiWrite fragmentation prevention and SSD optimization.
  • PerfectDisk 12.5 Home Premium provides automatic background defragmentation, OptiWrite for fragmentation prevention, SSD optimization, customizable scheduling options, patented file placement technology and boot time system file defragmentation. PerfectDisk 13.0 Home Premium is Microsoft certified for Windows 7.
  • PerfectDisk 13.0 Home Server eliminates Windows home server fragmentation, prevents fragmentation with OptiWrite, maximizes streaming media performance, reduces back up times, has seamless integration with the WHS Console and improves antivirus performance.

For Business

  • PerfectDisk 13.0 Professional for workstations, laptops and standalone PCs running Windows 8, Windows 7, Windows Vista, and Windows XP provides flexibility, control, and automation with its patented advanced SMARTPlacement optimization technology, OptiWrite fragmentation prevention and SSD optimization. It can also be centrally managed with the PerfectDisk Enterprise Console.
  • PerfectDisk 13.0 Server features patented advanced SMARTPlacement optimization technology and with free space consolidation to boost write performance, including OptiWrite for fragmentation prevention and a zero-fill feature to reclaim free space.
  • PerfectDisk 13.0 vSphere improves vSphere performance (VscsiStats) and is a complete host-based solution with unlimited guests that optimizes the physical host, guest machines, and storage solution to eliminate I/O throughput and I/O latency bottlenecks using virtualization awareness technology. This includes the optimization of both fat and thin provisioned virtual storage on both local and external RAID / SAN solutions.
  • PerfectDisk 13.0 Hyper-V is a complete host-based solution with unlimited guests that is proven to increase I/O throughput, and decrease I/O request latency. PerfectDisk 13.0 Hyper-V enables high performance for virtual machines and maximizes the performance of storage solutions using virtualization awareness technology.
  • PerfectDisk 13.0 Exchange automates the compaction and defragmentation of Exchange data stores to restore performance and disk space. It leverages all the capabilities of PerfectDisk 13.0 Server and supports Exchange Server 2010, 2007 and 2003.[9]
  • PerfectDisk 13.0 Enterprise Suite Console installs, deploys, configures, manages and reports on PerfectDisk 13.0 across computers, servers and virtual environments. PerfectDisk 13.0 Enterprise console also has the ability to customize up to 12 alerts on fragmentation of drives across the enterprise and allows customization of defragmentation schedules and virtual environments from a single location. The Enterprise Console can be integrated with Active Directory.

See also[edit]


  1. ^ PerfectDisk wins PC Magazine Editors' Choice, Windows IT Pro Readers' Choice, Redmond Magazine Readers' Choice,'s,'s and CHIPS Magazine's (Germany) 5-star awards, and Vector Users' Choice (Japan's largest download site) Award; see also Editor's Choice, PC Magazine May 24, 2005, 2004 and 2002; and Windows IT Pro Magazine, Cover Story: Readers' Choice Awards, Sept 2006 [1]
  2. ^ "Where Is All The Vista Software?" PC Magazine Feb 2007
  3. ^ US Patent number 5,398,142. Filing date: May 31, 1989. Issue date: Mar 14, 1995 [2]
  4. ^ Microsoft Windows Defrag and Diskeeper use several disk passes
  5. ^ The Backup Book: Disaster Recovery from Desktop to Data Center by Dorian J. Cougias, E. L. Heiberger, Karsten Koop - Schaser-Vartan Books 2003 (ISBN 0-972903-909)
  6. ^ "Whats-new-PD11-defrag". Retrieved November 9, 2010. 
  7. ^ Metadata defrag introduced in 1999
  8. ^ "SMARTPlacement" Patent number 5,398,142
  9. ^ "Storage". August 29, 2006. Retrieved November 9, 2010. 

External links[edit]