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Main Display |
iDefrag’s user interface is designed to be easy to understand without getting in your way. Unlike other disk defragmentation products, iDefrag shows both a view of the entire disk and the individual disk blocks; before iDefrag has read extent information covering an area of the disk, these blocks will be grey if used, and white otherwise. After reading extent information, iDefrag will color the blocks according to the class key, or use a shade of blue-grey to indicate that no class matches. If you watch the per-block display whilst iDefrag is reading extents from the disk, you will see the colors appearing as extents are classified.
The location indicators visible on the whole disk display will expand, if your screen is large enough or your disk small enough, to show the visible range. One other feature that is not displayed above is that during defragmentation, pairs of green and red arrows will appear alongside the location indicators, showing which area of the disk is currently being read from or written to; you can configure iDefrag’s display to track these, should you wish to, from the Preferences panel.
Drawing the full-color whole disk display is fairly processor intensive, so iDefrag will display a less colorful version when resizing the window, or before extent information has been completely read from the disk. Additionally, during defragmentation, you can configure how often the whole disk display is updated; users with slower machines may wish to reduce the frequency of updates to improve the program’s performance.
iDefrag also displays various statistics about the volume; these are updated as the program reads extent information from the disk, and show information about disk usage and fragmentation.
Note that it is difficult to arrive at a reasonable single measure of fragmentation, so iDefrag offers two different estimates in the form x%/y%, where the first number is the percentage of space outside the largest fragment, and the second number is a measure of the number of fragments per block. For free space, the second percentage is a measure of how many free space fragments there are with 100% indicating that every free block is not adjacent to another. The numbers under Volume Contents are averaged over the files, data forks and resource forks respectively.
There are many other possible ways of measuring fragmentation, and the most appropriate way to measure it is actually application specific because it depends on the pattern of disk accesses; as a result other disk utilities may provide quite different measures of fragmentation, and the percentage figures shown may or may not be an appropriate guide to the need to defragment any given disk.
In addition, once iDefrag has finished reading extents from the disk, it displays a list of the most fragmented files on the volume. The maximum number of files in the list can be configured from the Preferences panel (the default is 1,024), to prevent the list from using a lot of memory. You can select a file from the list to display more information about the file in the Info panel.
Note that the paths are displayed with “/” representing the root of the volume; to access the files from the Mac OS, you would need to prepend a path like “/Volumes/name of file system”, unless you are looking at the boot disk, in which case the paths will be the same. Some of the files displayed in the Files list may not be directly accessible from the Mac OS for one reason or another; these include file system metadata files as well as the files within the hidden folder “/HFS+ Private Data/” (note that the name of that folder is a little strange… it is quite possible to create a real folder of that name on a volume without interfering with the operation of HFS+).