GPFS-specific DMAPI events

The GPFS-specific events are not part of the DMAPI open standard. You can use these GPFS events to filter out events that are not critical to file management and to prevent system overloads from trivial information.

The DMAPI standard specifies that the system must generate ATTRIBUTE events each time the "changed time" (ctime) attribute for a file changes. For systems that write files in parallel, like GPFS, this generates ATTRIBUTE events from every node writing to the file. Consequently, it is easy for ATTRIBUTE events to overwhelm a data management server. However, the only ctime changes that are critical to GPFS are changes to either the permissions or ACLs of a file. In most cases, GPFS can ignore other ctime changes.

To distinguish file permission and ACL changes from other ctime updates, the following DMAPI metadata attribute events allow GPFS to filter ctime updates. Using these events, DM servers are able to track file permission changes without overwhelming the system with irrelevant ATTRIBUTE events. However, these events are not part of the CAE Specification C429 open standard and they were implemented specifically for GPFS systems.