You are configuring a Windows Server 2008R2 Hyper-V failover cluster. You configure five iSCSI logical unit numbers (LUNs) on shared storage, and you present them to the first server. Each LUN…

Question

Options

• AReset the iSCSI initiator name to the default name.
• BInstall and configure Microsoft Multipath I/O (MPIO).
• CIn the Disk Management console, rescan the disks.
• DIn the Disk Management console, configure shadow copies.

• A
  16% (3)
• B
  74% (14)
• C
  5% (1)
• D
  5% (1)

Explanation

Consider using multipath I/O software: In a highly available storage fabric, you can deploy failover clusters with multiple host bus adapters by using multipath I/O software. This provides the highest level of redundancy and availability. For Windows Server 2008 R2, your multipath solution must be based on Microsoft Multipath I/O (MPIO). Your hardware vendor will usually supply an MPIO device-specific module (DSM) for your hardware, although Windows Server 2008 R2 includes one or more DSMs as part of the operating system. Multipath I/O Overview Applies To: Windows Server 2008 R2 Multipathing Support for High Availability R 2008 includes many enhancements for the connectivity of a computer running a Windows server-class operating system to storage area networking (SAN) devices. Among the enhancements enabling high availability for connecting Windows-based servers to SANs is integrated Multipath I/O (MPIO) support. Microsoft MPIO architecture supports iSCSI, Fibre Channel and serial attached storage (SAS) SAN connectivity by establishing multiple sessions or connections to the storage array. Multipathing solutions use redundant physical path components--adapters, cables, and switches-- to create logical paths between the server and the storage device. In the event that one or more of these components fails, causing the path to fail, multipathing logic uses an alternate path for I/O so that applications can still access their data. Each network interface card (in the iSCSI case) or HBA should be connected by using redundant switch infrastructures to provide continued access to storage in the event of a failure in a storage fabric component. Failover times vary by storage vendor, and can be configured by using timers in the Microsoft iSCSI Software Initiator driver, or modifying the Fibre Channel host bus adapter driver parameter New MPIO features in Windows Server2008 include a Device Specific Module (DSM) designed to work with storage arrays that support the asymmetric logical unit access (ALUA) controller model (as defined in SPC-3), as well as storage arrays that follow the Active/Active controller model. Features of the included DSM The Microsoft DSM provides the following load balancing policies. Note that load balance policies are generally dependent on the controller model (ALUA or true Active/Active) of the storage array attached to Windows based computers. Failover No load balancing is performed. The application specifies a primary path and a set of standby paths. The primary path is used for processing device requests. If the primary path fails, one of the standby paths is used. Standby paths must be listed in decreasing order of preference (the most preferred path first). Failback Failback is the ability to dedicate I/O to a preferred path whenever it is functioning. If the preferred path fails, I/O is directed to an alternate path until function is restored to the preferred path, but I/O automatically switches back to the preferred path when function is restored. Round-robin The DSM uses all available paths for I/O in a balanced, round-robin fashion. Round- robin with a subset of paths The application specifies a set of paths to be used in a round-robin fashion, and a set of standby paths. The DSM uses paths from primary pool of paths for processing requests, as long as at least one of the paths is available. The DSM uses a standby path only when all primary paths fail. Standby paths must be listed in decreasing order of preference (most preferred path first). If one or more of the primary paths become available, DSM uses the standby paths in their order of preference. For example, given 4 paths--A, B, C, and D--A, B, and C are listed as primary paths, and D is standby path. The DSM chooses a path from A, B, and C in round-robin fashion as long as at least one of them is available. If all three fail, the DSM uses D, the standby path. If A, B, or C become available, DSM stops using D and switches to available paths among A, B, and C. Dynamic Least Queue DepthThe DSM routes I/O to the path with the least number of outstanding Weighted PathThe application assigns weights to each path; the weight indicates the relative priority of a given path. The larger the number, the lower the priority. The DSM chooses the path that has the least weight from among the available paths. The Microsoft DSM preserves load balance settings even after the computer is restarted. When no policy has been set by a management application, the default policy that is used by the DSM is either Round Robin, when the storage controller follows the true Active/Active model, or simple failover in the case of storage controllers that support the SPC-3 ALUA model. With simple Failover, any one of the available paths can be used as the primary path, and remaining paths are used as standby paths.

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