_dir_store files in the DS-System Online Storage


Creation Date: February 26, 2011
Revision Date: February 26, 2011
Product: DS-System

Summary

NOTE: Before reading this article, you should familiarize yourself with the concepts from the Knowledge Base article "_dirdesc files in the DS-System Online Storage".

The "_dir_store" feature consolidates the directory descriptor information (previously only contained in "_dirdesc" files) from all directories in a backup set. For backup sets with thousands of sub-directories, this can achieve performance improvements because the DS-System only needs to open the "_dir_store" file (and not all of the sub-folders' "_dirdesc" files).

You can determine if this feature is enabled by verifying if the "DirStoreSafeMode" parameter exists in the DS-Operator > Setup Menu > Advanced Configurations.

Details

By default, the "DirStoreSafeMode" parameter is enabled and DS-System will save directory metadata in two places: in the backup set's consolidated "_dir_store" and in each individual directory's "_dirdesc" file.

If the "DirStoreSafeMode" parameter is disabled, DS-System will only save the directory metadata to the backup set's "_dir_store" file.

When the DS-System needs a directory's descriptor information, it tries to scan the "_dir_store" file. If this fails, DS-System will try to scan the required directory's "_dirdesc" file (if it exists).

DS-System verifies a _dir_store file's validity every time it is accessed (except when it is automatically updated by a backup activity). Each _dir_store file contains a file signature and when the file is opened, the DS-System calculates the file signature and compares it to the one that it is stored inside the file. Similarly, every directory record in a _dir_store file has its own signature and in the event a record is missing or corrupted, it is repaired from either the "_dirdesc" file (if it exists) or when synchronization runs and updates the record with information from the DS-Client database.

See Also



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