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How the du command accounts for space usage

When you run the du command to check the disk space usage for a qtree or FlexVol volume mounted on a Linux client, the usage value might be higher than the value displayed by a quota report for the qtree or volume.

The output of the du command contains the combined space usage of all the files through the directory tree beginning at the level of the directory where the command is issued. Because the usage value displayed by the du command also includes the data blocks for directories, it is higher than the value displayed by a quota report.

Example of the difference between space usage accounted by the du command and a quota report​

The following quota report shows a limit of 10 MB for a qtree q1:
                                      ----Disk----  ----Files-----   Quota
  Volume   Tree      Type    ID        Used  Limit    Used   Limit   Specifier
  -------  --------  ------  -------  -----  -----  ------  ------   ---------
  vol1     q1          tree    user1   10MB   10MB       1       -   q1

...
In the following example, the disk space usage as the output of the du command shows a higher value that exceeds the quota limit:
[user1@lin-sys1 q1]$ du -sh
11M     q1