Dell Equallogic PS4110X PS4110 Hardware Owners Manual - Page 22

About Control Module Configurations, Single Controller Configuration

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Hardware Owner's Manual 3 Maintaining Control Modules • A release button and latch to release the control module from the array for replacement. The release lever has a switch that detects activation and prompts the array to save data to non-volatile storage, thereby protecting your data. Caution: Do not mix control module types in an array. Always make sure both control modules are the same type and color. See the latest PS Series Release Notes for information about other supported control modules. About Control Module Configurations While an array can run using only one control module, it is not recommended as this creates a single point of failure. If the control module fails and there is no other to take over, all access to your volumes stops until you replace it. Only one control module is active (serving network traffic) at one time. The secondary (redundant) control module mirrors cache data from the active control module. If the active control module fails, the secondary will take over network operations. Single Controller Configuration A single control module is a single point of failure. If the control module fails, the entire array (and all the volumes on it) becomes unavailable. Dell strongly recommends buying an array with two control modules, or installing a second control module in a single-controller array. In an array with a single control module, the module must be in slot CM0. Caution: For proper array cooling and airflow requirements, there must be a blank filler in the empty control module slot. Dual Controller Configuration A dual control module configuration eliminates a single point of failure in the array. If the active control module fails, the secondary control module takes over immediately with no interruption of service. This gives you time to replace the failed control module while your volumes and data remain accessible. In addition, a dual control module configuration supports a feature called vertical failover. An Ethernet port on the active control module can fail over to the same Ethernet port on the secondary control module if a network path fails. For example, if Ethernet 0 on CM0 loses connectivity (switch 0 fails), Ethernet 0 on CM1 takes over. Figure 14 illustrates the recommended configuration to support vertical failover. 18

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Hardware Owner's Manual
3 Maintaining Control Modules
•
A release button and latch to release the control module from the array for replacement. The release lever
has a switch that detects activation and prompts the array to save data to non-volatile storage, thereby pro-
tecting your data.
Caution:
Do
not
mix control module types in an array. Always make sure both control modules are the same
type and color. See the latest PS Series
Release Notes
for information about other supported control modules.
About Control Module Configurations
While an array can run using only one control module, it is not recommended as this creates a single point of
failure. If the control module fails and there is no other to take over, all access to your volumes stops until you
replace it.
Only one control module is active (serving network traffic) at one time. The secondary (redundant) control
module mirrors cache data from the active control module. If the active control module fails, the secondary will
take over network operations.
Single Controller Configuration
A single control module is a single point of failure. If the control module fails, the entire array (and all the
volumes on it) becomes unavailable. Dell strongly recommends buying an array with two control modules, or
installing a second control module in a single-controller array.
In an array with a single control module, the module must be in slot CM0.
Caution:
For proper array cooling and airflow requirements, there must be a blank filler in the empty control
module slot.
Dual Controller Configuration
A dual control module configuration eliminates a single point of failure in the array. If the active control module
fails, the secondary control module takes over immediately with no interruption of service. This gives you time to
replace the failed control module while your volumes and data remain accessible.
In addition, a dual control module configuration supports a feature called vertical failover. An Ethernet port on
the active control module can fail over to the same Ethernet port on the secondary control module if a network
path fails. For example, if Ethernet 0 on CM0 loses connectivity (switch 0 fails), Ethernet 0 on CM1 takes over.
Figure 14
illustrates the recommended configuration to support vertical failover.
18