Changing a volume's "owning controller" and "preferred controller" in Sun StorageTek[TM] Common Array Manager

Asset ID:	1-71-1006464.1
Update Date:	2011-02-25
Keywords:

Solution Type Technical Instruction Sure

Solution 1006464.1 : Changing a volume's "owning controller" and "preferred controller" in Sun StorageTek[TM] Common Array Manager

Applies to:

Sun Storage Flexline 380 Array
Sun Storage Common Array Manager (CAM) - Version: 5.0 and later    [Release: 5.0 and later]
Sun Storage 6180 Array - Version: Not Applicable to Not Applicable   [Release: N/A to N/A]
Sun Storage 6780 Array - Version: Not Applicable to Not Applicable   [Release: N/A to N/A]
Sun Storage 6580 Array - Version: Not Applicable to Not Applicable   [Release: N/A to N/A]
All Platforms

Goal

This document describes the significance of a volume's "owning controller" and "preferred controller", and also explains how these settings can be altered via the StorageTek [TM] Configuration Service or CAM Software., or SANtricity ES Storage Manager

Solution

Steps to Follow
Every volume built on an Sun StorageTek [TM] 6000/25x0 array line has two properties, a "preferred controller" and an "owning controller".

To determine what these are :

In the CAM software GUI, look at the Storage -> Logical -> Volumes screen, and click on the volume name to see it's Volume Details screen.

In SANTriciy software select the storage in Devices tab-> In the new window, select Logical tab-> select a volume in left pan

An example of how the information is reported is as follows :

Preferred Controller: A
* An owning controller must be chosen.: A

These arrays have two controllers, A and B, and although both are active, at any one time a single volume will be owned by one controller, and all I/O to that volume will be via the path(s) to that controller. Different volumes can be owned by different controllers to balance I/O to the array. The controller that currently owns the volume is referred to as its "owning controller".

A volume's "preferred controller" is the "controller of choice" for that volume. This is significant for a number of reasons, including :

After the reboot of an array, the volumes will be owned by their preferred controller.

Using the "Redistribute Volumes" button will move all volumes back to their preferred controller

CAM -> the Administration -> General Setup screen->Redistribute Volumes
SANtricity->array window->Advanced->recovery->Redistribute Volumes

An alert will be generated if a volume is transferred away from its preferred controller

If the multiple paths to the array are managed by STMS, the path(s) to the preferred controller will be classified as primary path(s), and the path(s) to the other controller will be classified as secondary path(s)

On the Volume Details screen only the owning controller is a user configurable setting - either the A or B controller can be selected, and if changed, this will cause a change of ownership of the volume to the other controller, with associated path failovers on the hosts connected to the array (provided multipathing software is correctly configured).

The volume ownership can be changed, as a consequence of changing the owning controller setting. If the current owning controller is the same as preferred controller, then changing the owning controller will also change the preferred controller to match. Here are all the possibilities :

CURRENT SETTINGS		CHANGE	RESULTING SETTINGS
Preferred Controller	Owning Controller		Preferred Controller	Owning Controller
A	A	Ownership to B	B	B
B	B	Ownership to A	A	A
A	B	Ownership to A	A	A
B	A	Ownership to B	B	B

If the current owning controller and preferred controller are different, and you want to change the preferred controller to match the current owning controller, the volume's ownership will need to be transferred twice, as follows :

CURRENT SETTINGS		CHANGE	RESULTING SETTINGS
Preferred Controller	Owning Controller		Preferred Controller	Owning Controller
A	B	Ownership to A THEN Ownership back to B	B	B
B	A	Ownership to B THEN Ownership back to A	A	A

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