You plan to deploy a distributed database Application that runs on Windows Server 2008 R2. You
need to design a storage strategy that meets the following requirements:
• Allocates storage to servers as required
• Isolates storage traffic from the existing network
• Ensures that data is available if a single disk fails
• Ensures that data is available if a single storage controller fails
What should you include in your design?

A.
An iSCSI disk storage subsystem that uses Microsoft Multipath I/O. Configure a RAID 0 array.

B.
An iSCSI disk storage subsystem that uses Virtual Disk Service (VDS). Configure a RAID 5 array.

C.
A Fibre Channel (FC) disk storage subsystem that uses Microsoft Multipath I/O. Configure a RAID 5

D.
A Fibre Channel (FC) disk storage subsystem that uses Virtual Disk Service (VDS). Configure a RAID
0 array.

Explanation:

MCITP Self-Paced Training Kit Exam 70-646 Windows Server Administration:
Fiber channel with isolate the network, Multipath I/O
Multipath I/O (MPIO) is a feature of Windows Server 2008 that allows a server to use multiple data
paths to a storage device. This increases the availability of storage resources because it provides
alternate paths from a server or cluster to a storage subsystem in the event of path failure. MPIO
uses redundant physical path components (adapters, switches, cabling) to create separate paths
between the server or cluster and the storage device. If one of the devices in these separate paths
fails, an alternate path to the SAN device will be used, ensuring that the server is still able to access
critical data. You configure failover times through the Microsoft iSCSI Software initiator driver or by
modifying the Fibre Channel HBA driver parameter settings, depending on the SAN technology
deployed in your environment.
If the server will access a LUN through multiple Fibre Channel ports or multiple iSCSI initiator
adapters, you must install MPIO on servers. You should verify that a server supports MPIO prior to
enabling multiple iSCSI initiator adapters or multiple Fibre Channel ports for LUN access. If you do

not do this, data loss is likely to occur. In the event that you are unsure whether a server supports
MPIO, only enable a single iSCSI initiator adapter or Fibre Channel port on the server.
Windows Server 2008 MPIO supports iSCSI, Fibre Channel, and Serially Attached Storage (SAS) SAN
connectivity by establishing multiple connections or sessions to the storage device. The Windows
Server 2008 MPIO implementation includes a Device Specific Module (DSM) that works with storage
devices that support the asymmetric logical unit access (ALUA) controller model as well as storage
devices that use the Active/Active controller model. MPIO also supports the following load-balancing
policies:
■Failover When this policy is implemented no load balancing is performed. The application specifies
a primary path and a group of standby paths. The primary path is used for all device requests. The
standby paths are only used in the event that the primary path fails. Standby paths are listed from
most preferred path to least preferred path.
■Failback When this policy is configured, I/O is limited to a preferred path while that path is
functioning. If the preferred path fails, I/O is directed to an alternate path. I/O will automatically
switch back to the preferred path when that path returns to full functionality.
■Round-robin All available paths are used for I/O in a balanced fashion. If a path fails, I/O is
redistributed among the remaining paths.
■Round-robin with a subset of paths When this policy is configured, a set of preferred paths is
specified for I/O and a set of standby paths is specified for failover. The set of preferred paths will be
used until all paths fail, at which point failover will occur to the standby path set. The preferred
paths are used in a round-robin fashion.
■Dynamic least queue depthI/O is directed to the path with the least number of outstanding
requests.
■Weighted path Each path is assigned a weight. The path with the least weight is chosen for I/O.
Load-balancing policies are dependent on the controller model (ALUA or true Active/ Active) of the
storage array attached to the Windows Server 2008 computer. MPIO is added to a Windows Server
2008 computer by using the Add Features item in the Features area of Server Manager.
MORE INFO More on MPIO
To learn more about Multipath I/O, consult the following TechCenter article:http
://www.microsoft.com/WindowsServer2003/technologies/storage/mpio/default.mspx.
■Striped with Parity This LUN type, also known as RAID-5, offers fault tolerance and improved read
performance, although write performance is hampered by parity calculation. This type requires a
minimum of three disks and the equivalent of one disk’s worth of storage is lost to the storage of
parity information across the disk set. This LUN type will retain data if one disk is lost, but all data
will be lost if two disks in the array fail at the same time. In the event that one disk fails, it should be
replaced as quickly as possible.