May 17, 2004, 12:00 AM — Now that you know all about the Virtual Disk Service (VDS) in Windows
Storage Server 2003, let's take an in-depth look at a technology called
Multipath I/O (MPIO).
MPIO allows you to have multiple paths to external storage components or
other NAS devices. Multipathing gives you the ability to build fully
redundant and persistent connections between storage devices and the
In actuality, MPIO is not a service provided by Windows Storage Server
2003, but more of a capability. To take advantage of this capability,
hardware vendors must develop the appropriate drivers using the Driver
Development Kit (DDK).
Microsoft's MPIO delivers a standard and interoperable path for
communication between storage products and Windows Server.
Additionally, multipathing allows a host to have up to a maximum of 32
paths to access an external storage device. This allows for hot
failover and load balancing between connections. Multipathing technology
is critical in ensuring highly available data to businesses.
If you are familiar with HP AutoPath or EMC PowerPath, then you are
already familiar with multipathing technology. Both HP and EMC have
developed multipathing drivers for their hardware such that you can
connect a Windows Storage Server 2003 NAS device to one of their
external NAS or SAN devices. This allows you the flexibility to grow
your systems in a customized manner, as well as grow into new
technologies while still leveraging existing investments in other
platforms and technologies.
By taking advantage of MPIO technology, you can have two fiber or
Ethernet gigabit controllers in your NAS device and have both of them
redundantly connected to an external storage device (such as your SAN).
With MPIO, one of these controllers can fail and the other one will
automatically take over the load, without any disruption to the