Sun Storage 6580 Array
 
Sun Storage Flexline 280 Array
 
Sun Storage 6180 Array
 
Sun Storage 2510 Array
 
Sun Storage 2540 Array
 
Sun Storage 6780 Array
 
Sun Storage 6140 Array
 
Sun Storage Common Array Manager (CAM)
 
Sun Storage 2530 Array
 
Sun Storage Flexline 380 Array
 
Sun Storage 6540 Array
 
Sun Storage Flexline 240 Array
 
Sun Storage 6130 Array
 

PLA-Support>Sun Systems>DISK>Disk Device Software>SN-DK: CAM
 

Applies to:

Goal

This document describes the significance of a volume's "owning controller" and "preferred controller", and also explains how these settings may be altered via the Sun Storage Common Array Manager software

Fix

Each volume created on an Sun StorageTek [TM] 6000/2500 array will have two different properties defined :

•  "owning controller"
•  "preferred controller"

To determine what these settings are :

In the CAM software GUI, look at the Volume Summary screen for the array, and click on a specific volume name to see it's Volume Details screen. The owning and preferred controller settings for that volume will be reported within this page.

Example :

Details



Name:					my-volume

World Wide Name:			60:08:0E:50:00:17:B9:DE:00:00:15:4C:4E:EF:4F:36

Type:					Standard

Capacity:				275.000 GB

Virtual Disk:				4

Pool:					data-pool

RAID Level:				5

Segment Size:				64 KB

Read Ahead Enabled:			True

Write Cache Enabled:			True

Write Cache With Replication Enabled:	True

Write Cache Without Batteries Enabled:	False

Write Cache Active:			True

Flush Write Cache After:		10s	

Disk Scrubbing Enabled:			True

					The setting will not take effect until disk scrubbing is enabled at the array level.

Disk Scrubbing With Redundancy Enabled:	False

					The setting will not take effect until disk scrubbing is enabled at the array level.

State:					Free

Condition:				Optimal

Status:					Online

Action:					Ready

Preferred Controller: B

Owning Controller: B

Modification Priority:			1-High

Security:				None

Pre-Read Redundancy Check Enabled:	False

Significance of these two settings :

The array has two controllers, A and B, and although both are active, at any time a specific volume will only be owned by one of those controller. All I/O to that volume will be via the host path(s) to only that controller. Different volumes may be owned by different controllers to balance overall I/O to the array. The controller that currently owns the volume is referred to as it's "owning controller"

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

• An alarm will be generated if a volume is not owned by it's preferred controller, and will persist until the volume is transferred back to being owned by it's preferred controller

• Using the "Redistribute Volumes" function will attempt to move all volumes back to their preferred controller. In the CAM GUI there is a button for this on the Administration screen for the array.

• After the reboot of an array, the volumes will start out being owned by their preferred controller.

• In host multipathing software the path(s) to the preferred controller will be classified as PRIMARY path(s) for a volume, and the path(s) to the alternate controller will be classified as SECONDARY path(s)

Modifying the "owning controller" and "preferred controller" settings of a volume :

In the CAM GUI, on the Volume Details screen, only the owning controller is a user configurable setting - either the A or B controller can be selected. If this is altered it will cause a change of ownership of the volume to the alternate controller. NOTE THAT MODIFYING THIS ARRAY SETTING MAY IMPACT VOLUME ACCESS OR REDUNDANCY ON THE ATTACHED HOSTS, depending on the configuration, host-type and multipathing drivers set-up, because a volume failover will occur.

The preferred controller setting cannot be changed directly, but it can be changed indirectly, as a consequence of changing the owning controller setting : IF THE CURRENT OWNING CONTROLLER IS THE SAME AS THE PREFERRED CONTROLLER, THEN CHANGING THE OWNING CONTROLLER WILL ALSO CHANGE THE PREFERRED CONTROLLER TO MATCH. Note that by changing this array setting the "primary path" designation for the volume will be altered from an array perspective, which may not be reflected automatically in host multipath driver configurations. This can cause a disagreement between the array and associated hosts on the preferred controller for a volume, which in turn may cause "Volume Not on Preferred Path" alarms.

The following table shows all possible modifications that may be performed :

Note that on lines 1 and 2 (where the current preferred controller and owning controller already match) modifying the owning controller changes BOTH the owning and preferred controller settings of the volume.

It is not possible to change only the preferred controller setting in CAM. Generally, if the current owning controller and preferred controller are different there will be a host path issue which needs to be resolved - please refer to <Document 1136186.1> Troubleshooting Sun StorageTek 2500, Sun Storage 2500-M2, Sun Storage 6000: Volume Not on Preferred Path

Rarely, there will be a configuration issue where the owning controller and preferred controller are different and you need to change the preferred controller setting on the array to match the current owning controller. In this scenario it cannot be done directly in CAM, but it may be achievable by modifying the volume's ownership twice, as follows :

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