Storage node

A Storage node represents a unit of storage such as an attached tape or disk drive. The type of storage is not mandated by the system; it can be physical, or logical.

Storage node lifecycle

The following section describes the scenarios in which a Storage node is created, updated or removed.

Creation/update

If a pattern triggers on a Directly Discovered Data node, such as a Discovered Tape Drive node, it can choose whether to specify keys for the Storage nodes it creates and maintains. If a key is specified then the decision whether to create a new Storage node or to update an existing one depends on the key. If a Storage node with the specified key exists, that node is updated, even if the node was previously maintained by a different pattern. In this case, the pattern takes over as the maintainer of the Storage node. If a node with the specified key does not exist, a new Storage node is created. In both cases, the Storage node is linked to the pattern with a maintainer relationship.

If a key for the Storage node is not specified by the pattern, the system creates or updates a group Storage with an automatically generated key. The key is based upon the key of the Host upon which the Storage is running, the specified type of the Storage and, optionally, a key group that can be used to separate the nodes into a number of groups. The count attribute is set to the number of instances in the group identified in the collection of Directly Discovered Data. Each time the host is scanned, the count attribute is changed to represent the number of instances seen in that scan.

Removal

A Storage node can be destroyed either manually or automatically.

To remove a Storage node manually, find the necessary Storage , select it in the list and pick Destroy from the Actions list.

Automatic removal happens according to the following scenario.
The age_count attribute of the Storage node contains information about when the Storage node was last confirmed by its maintaining pattern. If the age_count is positive, it represents the number of consecutive scans of the MFPart node in which the Storage was confirmed. If the age_count is negative, it represents the number of consecutive scans in which the Storage node was not confirmed. The last_update_success and last_update_failure attributes contain the date and time at which the Storage node was last confirmed, and not confirmed, respectively.

The default aging strategy only applies to Storage nodes created from patterns triggering on the following node kinds and maintaining the Storage nodes:

• DiscoveredTapeDrive
• DiscoveredDiskDrive

If the Storage is triggered on anything else, then aging must be implemented in the pattern using a removal block.

If the pattern does not have a removal block, Storage nodes are removed using an aging strategy based on the age_count and last_update_success attributes. The default aging parameters are the same as for a Software Instance node, that is, if a Storage node has not been seen for at least 7 scans, over a period of at least 10 days, it is destroyed.

If the pattern maintaining a node does have a removal block, the block can override the default aging scheme to destroy its nodes either earlier or later than normal. For TKU patterns, refer to the documentation accompanying each pattern for details of special removal behavior.

Regardless of the presence or absence of a removal block in the pattern, if the MFPart corresponding to a DDD-triggered Storage node is destroyed, the Storage node is immediately destroyed (see How nodes get removed).

Storage node attributes

The attributes on a Storage node are described in the tables below.

Storage node relationships

The relationships on a Storage node are described in the table below.