Since CommVault is hardware agnostic, even for Clustered Filesystem such as GPFS, Commvault will treat it like any other Disk Library.
It is however important to confirm from the hardware perspective, whether there are any limitation to the maximum usage of GPFS, as CommVault will use as much as possible during the Backup Operation (base on default settings), but if this exceeds the performance capavility of the GPFS, then it could result in performance degradation.
If there are no limitation on the hardware aspect, then it should be fine.
Note - if there are specific I/O requirement, you can then tune the maximum Reader/Writer within CommVault so it doesn't oer utilized.
Hopefully that helps