The CMS experiment workflows on StoRM based storage at Tier-1 and Tier-2 centers Cabrillo Bartolome I Cantabria Inst. of Phys. González-Caballero I Oviedo U. Sartirana A Ecole Polytechnique Matorras F Cantabria Inst. of Phys. Bonacorsi D INFN, Bologna 2009 Approaching LHC data taking, the CMS experiment is deploying, commissioning and operating the building tools of its grid-based computing infrastructure. The commissioning program includes testing, deployment and operation of various storage solutions to support the computing workflows of the experiment. Recently, some of the Tier-1 and Tier-2 centers supporting the collaboration have started to deploy StoRM based storage systems. These are POSIX-based disk storage systems on top of which StoRM implements the Storage Resource Manager (SRM) version 2 interface allowing for a standard-based access from the Grid. In this notes we briefly describe the experience so far achieved at the CNAF Tier-1 center and at the IFCA Tier-2 center. INTNOTECMSPUBL