Chapter 20 San Device Virtualization - HP Cisco MDS 9020 - Fabric Switch Configuration Manual

About SDV
S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m
Figure 20-1
Server
Figure 20-2
While most of the examples in this chapter describe target virtualization, the same behaviors apply to
Note
initiator virtualization as well.
Typically, today's deployments for handling device failures are designed for high availability (HA), with
redundancy being a key part of this design. Let's consider the case where a target is designed to be
redundant. Here, two arrays are deployed–a primary and secondary. Enterprises often use some type of
consistency technology (such as EMF SRDF) between the primary and secondary arrays to ensure that
the secondary is a mirrored copy of the production LUN. However, if the primary array fails, it must be
replaced by the secondary, as all I/O must occur on the secondary. Problems can occur because the time
required to bring the secondary array up and have it working often takes longer than most can afford
(Figure 20-3
Figure 20-3
Cisco MDS 9000 Family CLI Configuration Guide
20-2
Target Virtualization
Primary target
Virtual
target
Traffic from
server
Secondary target
Initiator Virtualization
Primary
initiator
Virtual
initiator
Traffic from
Secondary
initiator
illustrates this dilemma).
Typical Deployment for Handling Device Failures Before SDV
server
Chapter 20 SAN Device Virtualization
OL-16184-01, Cisco MDS SAN-OS Release 3.x