Go GPFS GO!
You are right! It is IBM’s crown jewels hidden away and locked in the deepest darkest dungeon! IBM does have literally hundreds of thousands of customers though and we don’t always hear about them. For every SONAS or V7000U system that IBM has sold, they have GPFS in them, so unbeknown to the end user they are using GPFS!
We work in the HPC space and, as one of the commenters here rightly points out, if you’re in this market you’ll hardly ever find a cluster without GPFS [it is not always sites with multiple PetaBytes of data either, but sites with complex storage environments that require strong data management]
We have also taken GPFS to a number of customers outside of HPC to dozens of private sector organisations for example WRN, RMS, IMD, Smoke and Mirrors and Landmark Solutions. Plus, many academic institutes such as University of Edinburgh, Technium Pembrokeshire and the University of Westminster. Go GPFS Go! David Yip, OCF