FAQ / What is mapmgr’s COMSTAR manager functionality?

Overview

Traditionally the mapmgr program’s basic functionality is to move the state of the views and logical units between nodes by zpool. Versions of mapmgr 3.6.0 and above will now also manage all the other COMSTAR objects. Any object that is not naturally associated with a zpool, i.e. not a view or a logical unit, will henceforth be referred to as “global objects” or just “globals”. The functionality of mapmgr splits into two main functions:

  1. Modification: To modify the state of globals, save this modification to disk, and synchronize this modification and it’s saved data cluster wide.
  2. Resynchronization: To synchronize nodes that have gone out of sync, perhaps due to one node being down for Maintenence.

Modification

Loosley speaking, if mapmgr is to be used as a clustered COMSTAR management tool, then when modification to the state of globals are made they ought to be made with the mapmgr subcommands rather than the stmfadm/itadm subcommands.  mapmgr adopts the same command line syntax as stmfadm/itadm.  Please see Fig 1. for the broad flow of execution when one of the subcommands for modifying globals is made.

Fig 1.

Resynchronization

Although mapmgr attempts to keep nodes in sync ‘on the fly’ it is possible the global objects between the nodes may go out of sync.  When this happens mapmgr will need to be called to attempt to resynchronize the nodes.  Please see Fig 2. for the flow of execution of this process.

Fig 2.

SN := Sequence Number.


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