An Analysis of Storage Interface Usages at a Large, MultiExperiment Tier 1

Abstract

Within WLCG much has been discussed concerning the possible demise of the Storage Resource Manager (SRM) and replacing it with different technologies such as XrootD and WebDAV. Each of these storage interfaces presents different functionalities and experiments currently make use of all of these at different sites. At the RAL Tier-1 we have been monitoring the usage of both SRM and XrootD by all the major experiments to assess when and if some of the nodes hosting the SRM should be redeployed to support XRootD. Initial results were previously presented which showed the SRM still handles the majority of requests issued by most experiments but with an increasing usage of XrootD, particularly by ATLAS. This updates these results based on several months of additional data and show that the SRM is still widely used by all the major WLCG VOs. We break down this usage according by read/write and by geographic source to show how a large Tier 1 is used globally. We also analyse usage by ‘use case’ (archival storage, persistent storage and scratch storage) and show how different experiments make use of the SRM.