An is a special that the uses to communicate management request information and event information between the and the in a storage array network environment.
The definition for the access volume is built into the configuration information. From the point of view of the host and the controllers, the access volume has a address. The default LUN is either 7 or 31. The access volume, however, does not have any drives assigned to the LUN.
You can manage a storage array in two ways:
For out-of-band management, the host sends data to the controller in the storage array over the host-to-controller interface cables. The storage management station sends commands to the controller through a separate Ethernet cable. Also, the controller sends events to the storage management station through the Ethernet cable. Commands and events are separate from the data.
For in-band management, the host sends data to the controller in the storage array through the host-to-controller interface cables. The storage management station also sends commands to the controller through the host-to-controller interface cables. The controller sends events to the storage management station through the host-to-controller interface cables. Commands and events are mixed with the data.
When commands and events are mixed with the data (in-band management), the storage management station and the controllers communicate by using a protocol called the Universal Transport Mechanism (UTM). The UTM protocol is a method through which commands are sent to the controller using standard block read and write.
For the in-band management method to operate, the storage array must have an access volume. The access volume provides the host operating system (OS) a procedure for finding the storage array. Without the access volume, the host OS cannot find a storage array that is connected to the host.
The access volume uses approximately 20 MB of storage space. The access volume storage space is not available for data storage.
In summary, the access volume has the following characteristics:
Attention:
Loss of management access – Removing an access volume causes loss of in-band management access from the host or host group with which the access volume is associated.
Attention:
Possible loss of data access – Removing an access volume can cause a loss of data access. The storage management station uses the access volume to communicate with a storage array. If you remove an access volume mapping from an in-band managed storage array, the storage management station can no longer access the storage array.
Note:
The access volume is not visible to the Linux operating system using the MPP failover driver.