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A manager is a process that runs on a storage module; it controls the following tasks for the entire Management Group:
- Data replication
- Keeps track of system status
- Coordinates reconfigurations as modules are brought up and taken offline
- Re-synchronize data when a module fails and recovers
Managers are storage modules within a Management Group that you designate to govern the activity of all of the storage modules in the group. All storage modules contain the management software, but you must designate which storage modules in the Management Group you want to act as managers. These storage modules “run” managers, much like a PC runs various services.
Management Groups are groups of storage modules within which one or more modules are designated as managers. The Management Group enables configuring one or more of the storage modules to act as the managers that control data transfer and replication. A quorum of managers is required to access the volumes. Loss of quorum does not mean loss of data, just loss of access.
A Management Group must have manager “quorum” or agreement of what is going on within the Management Group. Quorum is calculated based on the number of managers, for example if you have 3 storage modules, then all 3 should run as managers. The minimum number of managers to maintain quorum is two. With three mangers, if one storage module fails, two managers will still be operational and quorum is maintained. Data is unavailable until quorum can be reestablished.
Best Practice is to start between three and five managers to achieve best balance between fault tolerance and performance. Maintaining “quorum” refers to a design/implementation where a strict majority of managers are running at all times.
A virtual manager can be used in a configuration with two storage modules in the Management Group to maintain quorum in the event of a storage module failure.
On any even node number cluster or cluster with an even number of managers, you can right-click on the Management Group and add virtual manager. Then, in the event of a storage module failure that makes the Management Group loose quorum (loss of data access), you can right click on one of the surviving managers and select start virtual manager - this should restore quorum.
Note: You only start a Virtual Manager when it is needed to regain quorum in a Management Group.
A virtual manager:
- Is configured in the Management Group but is not started until the Management Group experiences a loss of quorum
- CANNOT be added after quorum has been lost
- Needs at least one regular manager to be running in the Management Group or geographical location
More information on Management Group manager configuration and use can be found in the Intel® Storage System SSR212MA Software User Manual.
This applies to:
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