Dell EqualLogic PS4110 Hardware Owner's Manual

Also see for PS4110: Hardware Overview Installation User guide

Dell EqualLogic PS4110 Hardware Owner's Manual Manual pdf 22 page image

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 leverhas 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 sametype and color. See the latest PS Series Release Notes for information about other supported control modules.About Control Module ConfigurationsWhile an array can run using only one control module, it is not recommended as this creates a single point offailure. If the control module fails and there is no other to take over, all access to your volumes stops until youreplace it.Only one control module is active (serving network traffic) at one time. The secondary (redundant) controlmodule mirrors cache data from the active control module. If the active control module fails, the secondary willtake over network operations.Single Controller ConfigurationA single control module is a single point of failure. If the control module fails, the entire array (and all thevolumes on it) becomes unavailable. Dell strongly recommends buying an array with two control modules, orinstalling 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 controlmodule slot.Dual Controller ConfigurationA dual control module configuration eliminates a single point of failure in the array. If the active control modulefails, the secondary control module takes over immediately with no interruption of service. This gives you time toreplace 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 onthe active control module can fail over to the same Ethernet port on the secondary control module if a networkpath 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