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Datastore Discovery

Datastore Discovery

A datastore is a storage object for virtual machines that are hosted on an ESX server.

A datastore is a collection of one or more physical disks, such as an iSCSI disk, and can be used by more than one ESX host. However, a physical disk can only connect to one datastore. Because ESX hosts can share datastores, it is easy to move virtual machine between hosts that have a common datastore.
Note: From the perspective of a virtual machine attached to a datastore, storage is provided by a single disk.
The advantages to connecting a datastore to multiple disks are:
  • The ability to mirror the disks for failover protection.
  • The ease of adding storage to the datastore.

For information about the tables used by Discovery to store the data for physical disks and their relationship to datastores and ESX hosts, see ESX server discovery.

In this example configuration, two ESX hosts share a common datastore that uses different types of storage.

Figure 1. Datastore Discovery with different storage types
Datastore Discovery

Relationships

ServiceNow provides tables that contain the relationships between an ESX host and its datastore and the specific disks to which the datastore is connected.

ServiceNow Discovery establishes the relationships between a datastore, the disks attached to the datastore, and the ESX server that hosts the virtual machines using that datastore. From the perspective of the ESX host, iSCSI and fibre channel disks connected to the datastore are treated as physical disks. Discovery does not show the direct relationship of the storage disks to the ESX host.

Note: Storage can be hosted on computers that are not discovered by Discovery. ESX hosts are discovered through vCenter, and storage is discovered separately through CIM. The system can only establish the relationship between the two when storage is discovered before ESX.
Table 1. Datastore tables
Table Description
cmdb_ci_vcenter_datastore_disk Stores the relationship of the physical disk to the datastore.
vcenter_datastore_hostmount Stores the relationship between the datastore and the ESX server to which it is connected.
cmdb_ci_disk Contains the physical disks connected directly to the datastore. This table also contains a reference to the ESX host.
cmdb_ci_fc_disk Contains the fibre channel disks in a storage area network (SAN) connected to the datastore. This table also contains a reference to the ESX host.
cmdb_ci_iscsi_disk Contains the iSCSI disks in an IP network connected to the datastore. This table also contains a reference to the ESX host.