Administrator Guide

Fault Domains in Legacy Mode
In Legacy Mode, each pair of primary and reserved ports are grouped into a fault domain. The fault domain determines which ports
are allowed to fail over to each other.
The following requirements apply to fault domains in legacy mode on a dual-controller Storage Center:
• A fault domain must contain one type of transport media (FC or iSCSI, but not both).
• A fault domain must contain one primary port and one reserved port.
• The reserved port must be located on a dierent controller than the primary port.
NOTE: For a single-controller Storage Center, only one fault domain is required for each transport type (FC or iSCSI)
because there are no reserved ports.
Failover Behavior
Legacy mode, ALUA port mode, and virtual port mode behave dierently during failure conditions because they use dierent
mechanisms to provide fault tolerance.
Scenario Virtual Port Mode Legacy Mode ALUA Port Mode
Normal operating
conditions
All ports are active and pass IO.
• Primary ports pass IO.
• Reserved ports remain in a
standby mode until a
controller failure.
• Active/Optimized ports pass
IO.
• Standby ports remain in a
standby mode until a
controller or port failure.
A controller fails in a dual-
controller Storage Center
Virtual ports on the failed
controller move to physical ports
on the functioning controller.
Primary ports on the failed
controller fail over to reserved
ports on the functioning
controller.
Active/Optimized ports on the
failed controller fail over to
Standby ports on the functioning
controller.
A single port fails (single-
or dual-controller Storage
Center)
An individual port fails over to
another port in the fault domain.
The port does not fail over
because there was no controller
failure. If a second path is
available, MPIO software on the
server provides fault tolerance.
The port fails over to the
Standby port on the functioning
controller.
Rebalancing Front-End Ports
If a controller has been added or taken oine, ports can become unbalanced. If local ports are unbalanced, you are prompted to
balance the ports by a message at the top of the Summary tab.
About this task
NOTE: Front-end ports are automatically rebalanced when using SCv2000 series controllers. Manual port rebalance is
not necessary.
Steps
1. Select a Storage Center from the Storage view. (Data Collector connected Storage Manager Client only)
2. Click the Summary tab.
3. In the banner message, click Rebalance Ports. The Rebalance Ports dialog box appears to display progress, and closes when
the rebalance operation is compete.
Managing Front-End IO Port Hardware
Front-end FC and iSCSI ports can be renamed and monitored with threshold denitions. iSCSI ports can be assigned network
conguration and tested for network connectivity.
For a Storage Center in virtual port mode, the Hardware tab displays a virtual port for each physical port. For physical ports, the
physical identity, speed, and hardware are given. For virtual ports, the current and preferred physical ports are shown.
Storage Center Maintenance
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