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5 Configuring and Deploying the Dell PS Series Multi-Path I/O Device Specific Module with Microsoft Windows | TR1036
1 Introduction
In our technology-driven world, data is one of the most valuable assets in any business organization.
Increasingly, organizations are requiring that their data be available 24 x 7. Continuous availability of data is
critical to all businesses. A data outage of any duration and size can result in a tremendous loss of revenue -
perhaps thousands or even millions of dollars. High availability is commonly achieved by using fault tolerant
and redundant components. For example, multiple servers may be used for redundancy, RAID or even
failover clustering on the servers, but this type of protection alone is not enough because it relies on a storage
area network (SAN) for its data. So, to ensure high availability, access to shared storage must be readily
available and protected against failure. As SANs become populated with more and more data, the potential
loss of access to data storage components becomes problematic. This is why many businesses today
consider MPIO a must.
1.1 MPIO
Microsoft Multi-Path I/O (MPIO) framework uses redundant physical (or virtual) connections to deliver high
availability to shared storage. Having multiple host connections, switches and SAN interfaces all help to
eliminate single points of failure. Using MPIO, servers can send multiple I/O streams to SAN volumes
concurrently. MPIO routes I/O over redundant paths that connect servers to storage and also manages these
paths so that requests can be re-routed through another path in the event of a failure in one of the
components along the way. MPIO also provides increased redundancy and can improve performance of
application data hosted on the SAN. See Figure 1.
Basic MPIO configuration and components
1: The eqldsm.sys kernel mode driver performs I/O path
selection and error handling
1
2: The EHCMservice.exe user mode service that
manages iSCSI sessions
1
3: Two or more 1 Gb or 10 Gb Ethernet NICs or HBAs
4: Two or more redundant physical paths to redundant
network switches
5: Two or more redundant physical paths provide a
network switch interlink (ISL)
6: Two or more redundant physical paths from the
network switches are connected to the separate
redundant controllers in each Member in a PS Series
Group.
7: Each Member in the Group has at least two physical
paths to the network switches that are connected to
separate redundant controllers.
1
This component is available when the Dell PS Series
MPIO DSM is installed.