PRIMECLUSTER Global Disk Services Configuration and Administration Guide 4.1 (Linux)

2.7.2.1 Shadow Class

A shadow class is the shadow object corresponding to a disk class that is an SDX object.

When disk classes and shadow classes do not have to be classified particularly, they may be called "classes" collectively.

Physical disks conforming to the following conditions can be registered with shadow classes.

• Disks registered with a class of GDS in another domain and managed as an SDX disk.
  If this applies, with one shadow class, a physical disk registered with the class that has the same name in another domain can be registered. When multiple physical disks are registered with one class in another domain, part or all of those disks can be registered with a shadow class. It is also possible to register part of those disks to a shadow class and the other to another shadow class.

In addition, the sizes of the private slices of physical disks to be registered with the same shadow class must be the same.

 

Attributes

A shadow class has the following attributes.

Name

This attribute identifies the shadow class in a system.

Type

This attribute indicates the type of shadow class. The following value is set.

Local

The object managed in a shadow class is available only on the current node.

Scope

This attribute indicates a group of nodes on which objects in the shadow class are available. The current node name is set.

 

Operation

The operations other than status display are not available from Management View. Use the command for each operation.

Create

A new shadow class will be automatically created by specifying a new class name when registering a disk with the sdxshadowdisk -M command.

Delete

The shadow class will be automatically deleted by deleting the last registered shadow disk from a shadow class with the sdxshadowdisk -R command.

Status Display

The shadow class status can be displayed with the sdxinfo command. A shadow class is indicated by 1 (one) in the SHADOW field for class information displayed with the sdxinfo -e long command.
For details about GDS Management View, see "Viewing Configurations and Monitoring Statuses."

 

Status

Unlike a disk class, there is no possibility that a shadow class is closed down.

 

Reference

There are the following points of concern for shadow classes.

Rules

Object Name

Number of Classes

Important Points

Operation in Cluster System

 

The disks that are registered with a class in a certain domain (domain alpha in the figure below) and accordingly are managed as SDX disks can be registered with a shadow class in another domain (domain beta in the figure below) connected to the same SAN.

[Figure: Example of Common Configuration with a Shadow Class]

 

Physical Device Name
The same physical device name (such as sda) is not necessarily assigned to the identical physical device in domain alpha and domain beta.