Chapter 21 San Device Virtualization - Cisco AP776A - Nexus Converged Network Switch 5020 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 21-1
Server
Figure 21-2
Note While most of the examples in this chapter describe target virtualization, the initiator virtualization
functions similarly.
Typically, today's deployments for handling device failures are designed for high availability (HA), with
redundancy being a key part of this design. Consider the situation where a target is designed to be
redundant. Two arrays are deployed–a primary and secondary in this situation. 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 because all I/O must occur on the secondary array. 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 21-3
Cisco MDS 9000 Family CLI Configuration Guide
21-2
Target Virtualization
Virtual
target
Traffic from
server
Secondary target
Initiator Virtualization
Primary
initiator
Virtual
initiator
Secondary
initiator
(Figure 21-3
Typical Deployment for Handling Device Failures Before SDV
Servers
Primary target
Traffic from
server
illustrates this dilemma).
I/O - Normal
SAN
I/O - After primary
failure
Chapter 21 SAN Device Virtualization
Primary
Device
Asychronous
Replication
Secondary
Device
OL-18084-01, Cisco MDS NX-OS Release 4.x