HP StorageWorks MSA2012i HP StorageWorks 2000 Modular Smart Array Reference Gu - Page 265
SAS Direct Attach Configurations
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SAS Direct Attach Configurations The SAS storage system uses Unified LUN Presentation (ULP). ULP is a controller software feature that enables hosts to access mapped volumes through both controllers' host ports (target ports) without the need for internal or external switches. In a dual-controller SAS system, both controllers share a unique node WWN so they appear as a single device to hosts. The controllers also share one set of LUNs to use for mapping volumes to hosts. A host can use any available data path to access a volume owned by either controller. The preferred path, which offers slightly better performance, is through target ports on a volume's owning controller. Note - Ownership of volumes is not visible to hosts. However, in SMU you can view volume ownership and change the owner of a virtual disk and its volumes. In the following configuration, both hosts have redundant connections to all mapped volumes. B0 WWN, A & B volumes A0 WWN, A & B volumes A1 WWN, A & B volumes A0 A1 B0 B1 B1 WWN, A & B volumes Figure 7-2 SAS Storage Presentation During Normal Operation (HighAvailability, Dual-Controller, Direct Attach with Two Hosts) Appendix C Host Access to Storage 265