atime values
atime is a standard file attribute that represents the time when the file was last accessed.
The file attribute atime is updated locally in memory, but the value is not visible to other nodes until after the file is closed. To get an accurate value of atime, an application must call subroutine gpfs_stat or gpfs_fstat.
You can control how atime is updated with the -S option
of the mmcrfs and mmchfs commands:
- -S no
- The atime attribute is updated whenever the file is read. This setting is the default if the minimum release level (minReleaseLevel) of the cluster is earlier than 5.0.0 when the file system is created.
- -S yes
- The atime attribute is not updated. The subroutines
gpfs_stat and gpfs_fstat return the time that the file system
was last mounted with -S no.Note: This setting can cause a problem if you have a file management policy that depends on the ACCESS_TIME attribute. For more information, see Exceptions to Open Group technical standards.
- -S relatime
- The atime attribute is updated whenever the file is read, but only if one
of the following conditions is true:
- The current file access time (atime) is earlier than the file modification time (mtime).
- The current file access time (atime) is greater than the atimeDeferredSeconds attribute. For more information, see mmchconfig command.
You can temporarily override the value of the -S
setting by specifying a mount option specific to IBM
Spectrum Scale when you mount the file system. The mount option
persists until the file system is unmounted. The following table shows how the mount options
correspond to the -S settings:
For more information, see Mount options specific to IBM Spectrum Scale.
| -S option of mmcrfs and mmchfs commands. | Equivalent mount option; persists until file system is unmounted. | Effect – see topic text for details. |
|---|---|---|
| no | norelatime | Allow atime to be updated. |
| yes | noatime | Do not allow atime to be updated. |
| relatime | relatime | Allow atime to be updated if a condition is met. |