Difference between pages "DFXML Piecewise Hashing" and "SuperFetch"

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m (<run> was renamed <byte_run>)
 
 
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[[:Category:Digital_Forensics_XML|Digital Forensics XML]] can be used to represent the results of piecewise hashing of individual files.  The [[md5deep]] suite now generates piecewise hashing results in DFXML when the <tt>-d</tt> option is provided.
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{{Expand}}
  
Here is an example:
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SuperFetch is a performance enhancement introduced in [[Microsoft]] [[Windows|Windows Vista]] to reduce the time necessary to launch applications. SuperFetch works with the memory manager service in Windows to analyze memory usage patterns over time to determine the optimal memory content for a given user for a date or time of day. This differs from the [[Prefetch]] technique used in Microsoft Windows XP, which preloads data into memory without analyzing usage patterns.
  
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From [http://msdn.microsoft.com/en-us/library/windows/hardware/dn653317(v=vs.85).aspx]: SuperFetch prioritizes the following kinds of pages to remain in memory:
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* Pages of applications that are used most frequently overall.
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* Pages of applications that are commonly used when resuming:
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** After extensive hibernation (for example, first thing in the morning).
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** After shorter periods of sleep or hibernation (for example, after lunch).
  
<pre>
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If SuperFetch detects that the system drive is a fast solid-state drive (SSD) (as measured by Windows Experience Index Disk score), then SuperFetch turns off [[ReadyBoot]].
<?xml version='1.0' encoding='UTF-8'?>
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<md5deep>
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<fileobject>
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<filename>sample/bar.txt</filename>
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<filesize>46</filesize>
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<mtime format='time_t'>1296497502.0</mtime>
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<byte_runs><byte_run file_offset='0' len='46'><hashdigest type='MD5'>0e886f6b08986269af98aedde53df23f</hashdigest><hashdigest type='SHA256'>21c35b5698f1e54d11ca8a41321d40d75797425013dfa1b640ab34d7efa7f1ac</hashdigest></byte_run>
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</byte_runs>
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<hashdigest type='MD5'>0e886f6b08986269af98aedde53df23f</hashdigest>
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<hashdigest type='SHA256'>21c35b5698f1e54d11ca8a41321d40d75797425013dfa1b640ab34d7efa7f1ac</hashdigest>
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</fileobject>
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<fileobject>
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<filename>sample/foo.txt</filename>
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<filesize>193</filesize>
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<mtime format='time_t'>1296497462.0</mtime>
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<byte_runs><byte_run file_offset='0' len='193'><hashdigest type='MD5'>06f63e03ed5e1770a2ff753a76d04906</hashdigest><hashdigest type='SHA256'>82a217a76ebe5e6c0f768576a3e8fd9ba6de504c42360c23e08ddfa22e711ba0</hashdigest></byte_run>
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</byte_runs>
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<hashdigest type='MD5'>06f63e03ed5e1770a2ff753a76d04906</hashdigest>
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<hashdigest type='SHA256'>82a217a76ebe5e6c0f768576a3e8fd9ba6de504c42360c23e08ddfa22e711ba0</hashdigest>
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</fileobject>
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<fileobject>
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<filename>sample/somedir/baz.txt</filename>
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<filesize>19</filesize>
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<mtime format='time_t'>1296497486.0</mtime>
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<byte_runs><byte_run file_offset='0' len='19'><hashdigest type='MD5'>362aa248563e453588755f280387a3d4</hashdigest><hashdigest type='SHA256'>7a7c62947561b0b00c213d37d04edbe0c8de46282098b7216a23b25fa336f150</hashdigest></byte_run>
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</byte_runs>
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<hashdigest type='MD5'>362aa248563e453588755f280387a3d4</hashdigest>
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<hashdigest type='SHA256'>7a7c62947561b0b00c213d37d04edbe0c8de46282098b7216a23b25fa336f150</hashdigest>
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</fileobject>
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</md5deep>
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</pre>
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[[Category:Digital Forensics XML]]
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== Configuration ==
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Because SuperFetch appears to leave a system with no available memory, some users turn it off to create the appearance of having more free memory. The feature can be configured by changing the <tt>HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PrefetchParameters\EnableSuperfetch</tt> [[Registry]] key [http://www.codinghorror.com/blog/archives/000688.html]. A value of zero disables SuperFetch, one enables it for booting only, two for applications, and three for both applications and boot. This setting can also be changed using the Services console, <tt>services.msc</tt> [http://tiredblogger.wordpress.com/2007/03/27/superfetch-not-so-super-for-gaming/].
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== File Formats ==
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Data for SuperFetch is gathered by the <tt>%SystemRoot%\System32\Sysmain.dll</tt>, part of the Service Host process, <tt>%SystemRoot%\System32\Svchost.exe</tt>, and stored in a series of files in the <tt>%SystemRoot%\Prefetch</tt> directory [http://www.microsoft.com/technet/technetmag/issues/2007/03/VistaKernel/]. These files appear to start with the prefix <tt>Ag</tt> and have a <tt>.db</tt> extension. The format of these files is not fully known, there is available unofficial partial specification [http://blog.rewolf.pl/blog/?p=214] and open source (GPL) dumper for .db files [http://code.google.com/p/rewolf-superfetch-dumper/]. Some information can be gleaned from these files by searching for [[Unicode]] [[strings]] in them.
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The SuperFetch feature is seeded with some basic usage patterns when the operating system is installed [http://channel9.msdn.com/showpost.aspx?postid=242429].
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== See Also ==
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* [[Prefetch]]
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* [[ReadyBoost]]
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* [[ReadyBoot]]
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* [[Windows SuperFetch Format|SuperFetch Format]]
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* [[Windows]]
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== External Links ==
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* [http://en.wikipedia.org/wiki/Windows_Vista_I/O_technologies#SuperFetch Wikipedia: Windows Vista I/O technologies - SuperFetch]
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* [http://channel9.msdn.com/showpost.aspx?postid=242429 Channel 9 Interview with Michael Fortin of Microsoft on SuperFetch]
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* [http://www.informationweek.com/news/showArticle.jhtml?articleID=196902178 Microsoft Predicts The Future With Vista's SuperFetch] from Information Week
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* [http://jessekornblum.com/presentations/dodcc08-2.pdf DC3 Presentation: My You Look SuperFetching], by Jesse Kornblum
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== Tools ==
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=== Open Source ===
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* [https://code.google.com/p/rewolf-superfetch-dumper/ rewolf-superfetch-dumper]
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[[Category:Windows]]

Revision as of 02:48, 24 April 2014

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Further information might be found on the discussion page.

SuperFetch is a performance enhancement introduced in Microsoft Windows Vista to reduce the time necessary to launch applications. SuperFetch works with the memory manager service in Windows to analyze memory usage patterns over time to determine the optimal memory content for a given user for a date or time of day. This differs from the Prefetch technique used in Microsoft Windows XP, which preloads data into memory without analyzing usage patterns.

From [1]: SuperFetch prioritizes the following kinds of pages to remain in memory:

  • Pages of applications that are used most frequently overall.
  • Pages of applications that are commonly used when resuming:
    • After extensive hibernation (for example, first thing in the morning).
    • After shorter periods of sleep or hibernation (for example, after lunch).

If SuperFetch detects that the system drive is a fast solid-state drive (SSD) (as measured by Windows Experience Index Disk score), then SuperFetch turns off ReadyBoot.


Configuration

Because SuperFetch appears to leave a system with no available memory, some users turn it off to create the appearance of having more free memory. The feature can be configured by changing the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PrefetchParameters\EnableSuperfetch Registry key [2]. A value of zero disables SuperFetch, one enables it for booting only, two for applications, and three for both applications and boot. This setting can also be changed using the Services console, services.msc [3].

File Formats

Data for SuperFetch is gathered by the %SystemRoot%\System32\Sysmain.dll, part of the Service Host process, %SystemRoot%\System32\Svchost.exe, and stored in a series of files in the %SystemRoot%\Prefetch directory [4]. These files appear to start with the prefix Ag and have a .db extension. The format of these files is not fully known, there is available unofficial partial specification [5] and open source (GPL) dumper for .db files [6]. Some information can be gleaned from these files by searching for Unicode strings in them.

The SuperFetch feature is seeded with some basic usage patterns when the operating system is installed [7].

See Also

External Links

Tools

Open Source