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AngeliaSyncTM - On-Line Help - Data Integrity Options
AngeliaSync offers several options designed to reduce the risk of corrupting data in your target folder and others that allow you to accept certain error conditions and treat them as warnings (NOTE - warnings allow processing of the current folder tree to continue while errors cause processing to be terminated immediately).
These options all effect processing in both Interactive and Automation modes. They are:
- Use "Safe Copy" Method When Updating Target Files - selecting this option causes AngeliaSync to create a temporary output file whenever it copies rather than overwriting any existing target file. Upon successful completion of the copy process for each file, the old target file (if any) is deleted and the temporary file is renamed in its place. Selecting this option avoids the possibility of a corrupt source file resulting in both the source and target copies of a file becoming unusable. We strongly recommend that this option be selected. The only significant "cost" of selecting this option is the requirement for space on the target device to temporarily house 2 copies of the file that is currently being copied. This may be a concern in the case of extremely large source files or target devices with very little free space. If this option is not selected, any previously existing target copy of a source file will be directly overwritten when it is updated.
- Use "Verified Copy" Method When Updating Target Files - any time that data is moved from place to place there is a chance that a hardware failure will cause corruption of the data being moved. In an effort to identify these instances before they become critical, AngeliaSync offers a "Verified Copy" method that will detect certain types of errors with a very small penalty in processing time (our testing indicates about a 10% increase in total processing time). If the "Verified Copy" option is selected, each time data is read from the source file and written to the target file, the program immediately reads back the data just written to the target and compares it to the source. If there is any discrepancy an error is generated and processing is stopped. Note that due to caching algorithms used by many disk devices this may not detect errors on the target disk, but it is still likely to detect errors that occur between the source device and the target controller (in particular, it is likely to detect errors that occur during network copy operations that are due to data transmission errors). If "Safe Copy" is employed, and an error is detected, the process will halt before the deletion of the previous target copy.
- Use "Copy Then Verify" Method When Updating Target Files - any time that data is moved from place to place there is a chance that a hardware failure will cause corruption of the data being moved. In an effort to identify these instances before they become critical, AngeliaSync offers a "Copy Then Verify" method that will detect most types of errors but at a significant cost in processing time (our testing indicates about an 80% increase in total processing time - ie almost double). If the "Copy Then Verify" option is selected, each target file is read back after it has been completely written and is compared to the source file. If there is any discrepancy an error is generated and processing is stopped. This technique is far less likely to be fooled by disk caching algorithms and so provides a somewhat greater degree of security in return for a somewhat greater investment in processing time. If "Safe Copy" is employed, and an error is detected, the process will halt before the deletion of the previous target copy.
- Busy Source File Generates A Warning Instead Of An Error - If any source file is in use by another application, and that application has forbidden sharing of the file by other readers, AngeliaSync will not be able to process that source file. The normal consequence of this situation is to generate an error and immediately stop further processing. However, in some instances, you may be willing to risk skipping some file(s) in a folder tree while updating the remaining "non-busy" files. Selecting this option will cause AngeliaSync to treat busy source files as a warning event instead of an error. Warning Events are noted in the progress report but they allow processing of the current source folder tree to continue. If this option is not selected, encountering a busy source file will cause AngeliaSync to generate an error and immediately stop any further processing.
- Lack Of Space On Target Generates A Warning Instead Of An Error - AngeliaSync always checks the status of the target device before copying each file to be sure that there is enough room on the target device to complete the copy of that file. If there is not enough free space to accomodate the target (and space requirements will vary depending on the selection of "Safe Copy"), then AngeliaSync will normally generate an error and stop processing. Selecting this option will cause AngeliaSync to treat this "Insufficient Space On Target" as a warning event rather than an error. Warning Events are noted in the progress report but they allow processing of the current source folder tree to continue. If this option is not selected, lack of space on the target device will cause AngeliaSync to generate an error and immediately stop any further processing. Note - this option applies to circumstances in which the lack of space on the target device is detected prior to beginning the copy of a particular source file. It is possible for the free space on the target to become insufficient at some time after AngeliaSync has begun to copy the file. In this case, if AngeliaSync is unable to complete writing the current file because it runs out of space, an error will be generated regardless of this setting.