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JSI Tip 0788. New SP4 CHKDSK switches.

SP4 adds a /C and / switch to CHKDSK.

I The /C switch directsCHKDSK to skip the checks that detect cycles in the directory structure. Cycles are a very rare form of corruption in which a subdirectory has itself for an ancestor. Using the /C switch can speedCHKDSK by about 1 to 2 percent. Using /C can also leave directory "loops" on an NTFS volume. Such loops may be inaccessible from the rest of the directory tree and could result in some number of files being orphaned in the sense that they cannot be seen by any Win32 applications -- including backup applications.

The /I switch directsCHKDSK to skip checks that compare directory entries to the FRSs that correspond to those entries. Thus, while the directory entries are still checked to be sure that they are self-consistent, they are not necessarily consistent with the data stored in their corresponding FRSs even afterCHKDSK has run with this switch in effect. Using the /I switch typically results inCHKDSK times being reduced by 50 to 70 percent. Exactly how much fasterCHKDSK is with this switch will depend on factors such as the ratio of files to directories, as well as on the relative speed of disk I/O versus CPU speed, and is, therefore, difficult to predict in advance. The use of the /I switch can result in directory entries remaining that refer to incorrect FRSs or in FRSs remaining that are not referenced by any directory entry. The later case is another form of orphaning. The file represented by the FRS may be intact in all ways except for the fact that it is invisible to all Win32 applications-including backup applications. In the former case, files may appear to exist; yet applications encounter errors when attempting to access them.

When the systems detects disk corruption, you have 3 choices:

1. Do nothing now, run a full CHKDSK when you have time. (I recommend option 3 instead).

2. Run a full CHKDSK with the /F and possibly the /R switches.

3. Run an short CHKDSK the /C and/or the /I switches and subsequently run a full CHKDSK.

For a complete explanation of CHKDSK and the new switches, see Q187941.

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