PRIMECLUSTER Global Disk Services Configuration and Administration Guide 4.1 (Solaris(TM) Operating System)

2.7.2.3 Shadow Group

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

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

To access data on a logical volume through a shadow volume, a shadow group must be created in the same configuration as that of the disk group to which the logical volume belongs. The following configurations must be identical.

• Group type. This can be viewed in the TYPE field displayed with the sdxinfo -G -e long command.

• Disks constituting the group and disks constituting the lower level group. The disk unit's copy function destination disk is also available. These can be viewed with the sdxinfo -D command and the sdxinfo -G command.

• Order of connecting disks and lower level groups when the group is the stripe type or the concatenation type. This can be viewed in the DISKS field displayed with the sdxinfo -G command.

• Stripe width when the group is the stripe type. This can be viewed in the WIDTH field displayed with the sdxinfo -G -e long command.

In addition, a shadow volume can be created by connecting only one of the following disks to a shadow group of the mirror type, and thus data on a single volume or on a slice temporarily detached can be accessed.

• Single disk. The disk unit's copy function destination disk is also available.

• Disk containing a slice temporarily detached (in the TEMP status). The disk unit's copy function destination disk is also available.

   

Attributes

A shadow group has the following attributes.

Name

This attribute identifies the shadow group within a shadow class.

Type

This attribute indicates the type of shadow group. One of the following values can be set.

mirror

Shadow disks and lower level shadow groups belonging to the shadow group will be mirrored to one another. A maximum of 8 disks and lower level shadow groups may be connected to a shadow group in total. In other words, a maximum of eight-way multiplex mirroring is supported.

stripe

Shadow disks and lower level shadow groups connected to the shadow group will configure stripe columns respectively and will be striped. Since a maximum of 64 shadow disks and lower level shadow groups can be connected to a shadow group in total, striping across a maximum of 64 columns is supported.

concat

Shadow disks connected to the shadow group are concatenated. Since a maximum of 64 shadow disks can be connected to a shadow group, a maximum of 64 shadow disks can be concatenated.

Stripe Width

This is an attribute of shadow groups of the "stripe" type, which indicates the data unit size when data is striped.

 

Operation

The operation other than status display from Management View is unsupported. Use the command for each operation.

Create

A shadow group (higher level) will automatically be created by specifying a new (higher level) shadow group name when connecting a shadow disk with the sdxshadowdisk -C command, or connecting a shadow group with the sdxshadowgroup -C command.

Delete

The shadow group (higher level) will be automatically removed by disconnecting the only remaining shadow disk with the sdxshadowdisk -D command, or by disconnecting the only remaining lower level shadow group with the sdxshadowgroup -D command. You can also delete a shadow group with the sdxshadowgroup -R command.

Connect

A shadow group will be added to another shadow group with the sdxshadowgroup -C command. A shadow group that is connected to another shadow group is particularly called a lower level shadow group, and a shadow group to which another shadow group is connected is particularly called a higher level shadow group.

Disconnect

The lower level shadow group will be disconnected from the higher level shadow group with the sdxshadowgroup -D command.

Status Display

The shadow group status can be displayed with the sdxinfo command. For details on GDS Management View, see "Viewing Configurations and Monitoring Statuses."

 

Reference

There are the following points of concern for shadow groups.

Rules

Number of Groups

Creating Group Hierarchy