ScanDir


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About performance...
Back in 1998, when the first version of ScanDir was written, there were no DVD's or USB sticks, only CD's with a maximum capacity of 650 Mb, a really big harddisk could hold 20 Gb and the maximum harddisk size supported by Windows98 was 64 GB. The number of directories (folders) and the number of files on a harddisk or CD were limited. ScanDir keeps its data in-memory. With today's storage capacity where drive space is measured in Tb (1000 Gb) data kept in memory can rapidly grow. For ScanDir this means that performance can degrade noticeably:
  • when the number of directories in the Directory Tree increases;
  • when the number of files that match the search criteria increases;
Fortunately there are several ways to reduce the memory used by ScanDir and thus improve performance.

Limit the number of directories in the Directory Tree.
ScanDir stores directory/folder names in a Windows control called: TreeView. Only the names of expanded directories (and their sub-directories) are kept here. Collapsing directories (right-click, Collapse all) will reduce the resources used by the TreeView component and increase ScanDir's performance. One special directory uses extremely much resources: C:\Windows\. It is highly recommended to keep this folder collapsed when possible.

The option "Expand All" from the Dir.Tree PopUp menu should be used with care and preferrably not on "This PC" or on a root directory (drive).

Limit the number of files scanned.
The number of files scanned can be limited by specifying directries to be bypassed for scanning. They can be specified in the Skip list: right-click a directory in the Dir.Tree and select "Add to Skip" from the PopUp menu or select the [Skip] tab, right-click and choose 'Add directory' from the PopUp menu. It is recommended to add the following files to the Skip list:
  • C:\Windows\
  • C:\Windows.old\
  • C:\Program files\
  • C:\Program files (x86)\
The Item limit parameter (Configuration, Advanced) can be used generate a warning message when a Scan produces (too) many results. The default value for Item Limit= 50000. When the Scan Limit is reached, a message is displayed, asking to Continue (Yes / No).

Other options.
The StopIntvl parameter (Configuration, Advanced) specifies how often ScanDir processes Windows interrupts. The recommended value is 100. This is also the default value for ScanDir 1.3.3 and later, older versions (or new versions using old settings) have a default of 10000.

The option Show Progress makes ScanDir slower. For maximum performance uncheck [-] Show Progress in Configuration, Interface. Show Progress updates the Status bar for every directory that is scanned.

The option Calculate directory size makes ScanDir a lot slower. For maximum performance uncheck [-] Calculate directory size in Configuration, Advanced. Calculate directory size reads all files in a directory (and all it's sub-directories) to calculate the total directory size.

If you expect a very large number (hundreds of thousands) of Scan results and you ony want the list of files, it is possible to write the results directly to an output textfile, bypassing internal ScanDir processing: Select "Scan to File" from the File or PopUp menu. This will write a textfile containing all filenames that match the Scan argument(s), the Item list is not used (ScanDir automatically switches to the Log tab) and operations like Copy, Rename, Delete... etc. are not available. It is recommended to (temporary) turn OFF "AutoScan" when "Scan to File" is used.






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