## 6 Performance Evaluation
### Directory Activation Experiment  
The second scenario is a directory activation experiment opposite to the first scenario. During the first 3 days of the entire experimental period (6 days), no file access is performed,  
Figure 11: Change of local storage usage of active file mode change mechanism according to _USRT_ in directory deactivation scenario. (**a**) usrt-0. (**b**) usrt-0.1. (**c**) usrt-0.2. (**d**) usrt-0.3. (**e**) usrt-0.4. (**f**) usrt-0.5. (**g**) usrt-0.6. (**h**) usrt-0.7. (**i**) usrt-0.8. (**j**) usrt-0.9. (**k**) usrt-1.0. and the directory is kept inactive. Then, the directory is activated by performing periodic file access during the latter 3 days. The experiment starts with all 10 test files in the synchronization directory in the online mode. During the initial directory deactivation period, we recorded only the current local storage usage for each file access cycle. In the latter half of the directory activation period, each file is accessed one by one in a 7-h cycle. The file access method depends on the file mode, as with the first experiment. For the local mode file, we copied the same test file in the temporary directory to the synchronization directory. For the online mode file, we first changed it to the local mode. In this experiment, we measured the local storage usage and the file access cost while the directory is transitioned from the inactive to active state. To analyze the effect of changing parameters on the local storage usage and file access cost, the active file mode change mechanism conducted the experiment by changing the three threshold values of elapsed time since the last access threshold (_DSLAT_), local mode threshold (_LMT_), and used storage ratio threshold (_USRT_). In the case of the _LMT_, as in the previous experiment, it was set to the same value as the _OMT_. Figure 12 shows the results of measuring changes in the local storage usage when the manual file mode change mechanism is applied to the directory activation scenario. Since there is no access operation during the initial period of directory deactivation, all files in the directory remain in the online mode while keeping the local storage usage to a minimum. During the latter period of directory activation, the experiment begins periodically accessing files one by one in sequence. Since all files are in the online mode when accessed for the first time, the local storage usage increases in the order in which files are changed to the local mode. After all 10 files have been accessed, the storage usage becomes 10 MB, which is 100% of the total storage. The manual file mode change mechanism minimizes the local storage usage during directory deactivation periods when all files are in the online mode, but each time the file is accessed, the access cost increases as the original file is downloaded from the server to change to the local mode. Figure 13 shows the change in the local storage usage of the active file mode change mechanism according to the change of the _DSLAT_, which is the elapsed time threshold since the last access. First, looking at the initial directory deactivation period, unlike the manual file mode change mechanism, the storage usage is already about 5 MB and 6 MB. We can see that about half of the files have already been changed to the local mode when the experiment starts. As soon as the experiment started with all test files in the online  
Figure 12: Change of local storage usage of manual file mode change mechanism in directory activation scenario. mode, the local mode change operation was performed because the directory activation ratio calculated by the active file mode change mechanism was greater than the local mode threshold (_LMT_) default value of 0.5. Because the _USRT_ was set to the default value of 0.5, the files were changed to the local mode until the storage usage ratio became greater than 50%.