External storage system configuration details (Fibre Channel)
Plan for your external storage system configurations through Fibre Channel connections with IBM Spectrum Virtualize™ clustered systems.
See the following website for the latest support information:
All IBM Spectrum Virtualize nodes in a system must be able to connect to the same set of storage system ports on each device. A system that contains any two nodes that cannot connect to the same set of storage-system ports is considered degraded. In this situation, a system error is logged that requires a repair action. This rule can have important effects on a storage system such as an IBM® DS4000® series controller, which has exclusion rules that determine to which host bus adapter (HBA) worldwide node names (WWNNs) a storage partition can be mapped.
A storage-system logical unit (LU) must not be shared between the system and a host.
You can configure certain storage systems to safely share resources between the IBM Spectrum Virtualize system and direct-attached hosts. This type of configuration is described as a split storage system. In all cases, it is critical that you configure the storage system and SAN so that the IBM Spectrum Virtualize system cannot access logical units (LUs) that a host or another IBM Spectrum Virtualize system can also access. This split storage system configuration can be arranged by storage system logical unit number (LUN) mapping and masking. If the split storage system configuration is not guaranteed, data corruption can occur.
Besides a configuration where a storage system is split between a IBM Spectrum Virtualize system and a host, the IBM Spectrum Virtualize system also supports configurations where a storage system is split between two IBM Spectrum Virtualize systems. In all cases, it is critical that you configure the storage system and SAN so that the IBM Spectrum Virtualize system cannot access LUs that a host or another IBM Spectrum Virtualize system can also access. You can use storage system LUN mapping and masking to arrange for this configuration. If this configuration is not guaranteed, data corruption can occur.
Unsupported storage systems
When a storage system is detected on the SAN, IBM Spectrum Virtualize attempts to recognize it using its Inquiry data. If the device is not supported, the system configures the device as a generic device. A generic device might not function correctly when it is addressed by a IBM Spectrum Virtualize system, especially under failure scenarios. However, the system does not regard accessing a generic device as an error condition and does not log an error. Managed disks (MDisks) that are presented by generic devices are not eligible to be used as quorum disks.
Split storage-system configuration details
The system is configured to manage LUs that are exported only by RAID storage systems. Non-RAID storage systems are not supported. If you are using IBM Spectrum Virtualize to manage flash drive or other JBOD (just a bunch of disks) LUs that are presented by non-RAID storage systems, the system itself does not provide RAID functions. Consequently these LUs are exposed to data loss in the event of a disk failure.
If a single RAID storage system presents multiple LUs, either by having multiple RAID configured or by partitioning one or more RAID into multiple LUs, each LU can be owned by either the system or a direct-attached host. LUN masking must also be configured to ensure that LUs are not shared between IBM Spectrum Virtualize nodes and direct-attach hosts.
In a split storage-system configuration, a storage system presents some of its LUs to a IBM Spectrum Virtualize system (which treats the LU as an MDisk) and the remaining LUs to another host. The IBM Spectrum Virtualize system presents volumes that are created from the MDisk to another host. There is no requirement for the multi-pathing driver for the two hosts to be the same. Figure 1 shows that the RAID storage system could be an IBM DS4000, for example, with RDAC used for pathing on the directly attached host, and SDD used on the host that is attached with IBM Spectrum Virtualize. Hosts can simultaneously access LUs that are provided by the system and directly by the device.
