Key Concepts; Automatic Failover And Fallback; Configuring Sdv - Cisco AP776A - Nexus Converged Network Switch 5020 Configuration Manual

Configuring 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

Key Concepts

The following terms are used throughout this chapter:
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Automatic Failover and Fallback

As of Cisco MDS NX-OS Release 4.1(1a), SAN device virtualization supports automatic failover and
fallback configurations for the virtual devices. In all of the earlier releases, when there was a failure, you
needed to manually configure the device as primary to make it active. With the introduction of automatic
failover and fallback configurations, the active device is distinguished from the primary device indicated
by a (*) symbol.
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To configure automatic failover, use the attribute failover auto command in SAN device virtualization
configuration mode. To configure automatic failover and fallback, use the attribute failover auto
fallback command. To identify the active device, use the show sdv database command.
Configuring SDV
SDV is a distributed service and uses Cisco Fabric Services (CFS) distribution to synchronize the
databases. When you configure SDV, it starts a CFS session and locks the fabric. When a fabric is locked,
Cisco NX-OS software does not allow any configuration changes from a switch other than the switch
holding the lock–and issues a message to inform users about the locked status. Configuration changes
are held in a pending database for the application. You must perform a commit operation to make the
configuration active and to release the lock for all switches. You can discard or stop changes from being
distributed by entering the abort or clear command.
See
Cisco MDS 9000 Family CLI Configuration Guide
21-4
Virtual device—The virtualized or proxy representation of the real device, which is registered with
the name server and has a pWWN and FC ID. A virtual device exists as long as its real (physical)
counterpart is online. The virtual device pWWN and FC ID must be unique and cannot clash with
any real device pWWNs and FC IDs.
Virtual domain—Reserved by SDV to assign FC IDs to virtual devices. If the switch that reserved
the domain goes down, another switch takes over its role using the same domain.
Primary device—The device that is configured as primary. By default, the primary device becomes
the active device if it is online.
Secondary device—The additional device that is configured. By default, the secondary device is
standby.
Active device—The device that is currently virtualized is called the active device. By default, the
primary device becomes the active device if it is online. The active device is indicated by a (*)
symbol.
Auto failover—When there is a failure, the failover auto attribute automatically shuts down the
primary device and brings up the secondary device to active state. When the primary device comes
back online, it requires user intervention to switchover.
Auto failover with fallback—In addition to automatic failover, when the primary device comes back
online after a failover, the primary device is brought to active state and the secondary device moved
to standby state.
Chapter 7, "Using the CFS Infrastructure"
Chapter 21
for more details about CFS,
OL-18084-01, Cisco MDS NX-OS Release 4.x
SAN Device Virtualization