Discovering resources

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After you add the various HMCs, hosts, host groups, and storage subsystems to the KSYS subsystem for disaster recovery management, you must run the ksysmgr discover command to discover all the hosts that are managed by the HMCs in both the home and the backup sites. During the discovery process, the KSYS subsystem captures the configuration information of the home site and its relationship with the backup site and prepares the backup site to perform disaster recovery operations later.

During the initial discovery operation, the KSYS subsystem uses this configuration information to gather the list of VMs from all the host groups across sites and the corresponding disks for disaster recovery management. During any subsequent discovery operations, the KSYS subsystem scans the environment for any changes to the environment (for example, addition of a new VM, addition of a disk to VM, Live Partition Mobility (LPM) movement of a VM from one host to another host, and so on) and adapts to the modified environment.

The KSYS subsystem interacts with the HMC to retrieve the details about the disks of each VM and to check whether the VMs are currently set up for the storage devices mirroring. If the disks are not set up for mirroring properly, the KSYS subsystem notifies you about the volume groups that are not mirrored. All volume groups of a VM must be mirrored. Disks can be available over N-Port ID Virtualization (NPIV), virtual SCSI (vSCSI), and combination of both these modes.

The KSYS subsystem identifies and stores the Universally Unique Identifier (UUID) of the boot disk for each virtual machine during the discovery operation. The KSYS subsystem also stores the information about the corresponding replicated boot disks in the backup site. When you initiate a disaster recovery operation, the KSYS subsystem uses this information to boot the virtual machines with the corresponding boot disks on the paired host in the backup site. For example, if a virtual machine in the home site has multiple bootable disks, the KSYS subsystem restarts the virtual machine by using the corresponding boot disk in the backup site.

Note: The VM Recovery Manager DR identifies and stores the boot disk information only for POWER8®, and later processor-based servers. The VM Recovery Manager DR solution requires HMC Version 9 Release 9.1.0, or later to support this feature. If your production environment contains an older version of the host or HMC, the KSYS subsystem cannot store the boot disk information and the virtual machines will restart in the backup site by using the first disk in the System Management Services (SMS) menu.

If the configuration is modified, for example, if a logical partition or a storage device is added, the KSYS subsystem rediscovers the home site, identifies the changes in the configuration, and marks the changes in its registries. The KSYS subsystem monitors this new environment for any disaster situations.

Note: For EMC storage subsystem, the Gatekeeper and Access Control Logix (ACLX) devices are ignored by the KSYS node during the discovery operation.

By default, the KSYS subsystem automatically rediscovers sites once in every 24 hours at midnight (00:00). You can change the time at which this automatic rediscovery is run by modifying the auto_discover_time attribute. However, if you modified the configuration by adding or removing any resource, and you want the KSYS subsystem to rediscover the resources immediately, you can manually run the ksysmgr discover command. If you run the discovery operation for a site, the KSYS subsystem might take a few minutes to discover all virtual machines from all the host groups across both the sites and to display the output. To save time, you can run the discovery operation for a specific host group that contains the hosts that you modified.

After a virtual machine migrated within a site or across the sites, and multiple disk is used, you must run the discovery operation manually. If you do not run the discovery operation manually, the periodic discovery suffices for the need of running discover manually.

Tip: To avoid configuration information loss on the KSYS node because of any node failure events, back up your current configuration settings as a snapshot after you complete the initial configuration of sites, hosts, host pairs, host groups, HMCs, and storage devices.

To discover resources in the KSYS configuration settings, complete one of the following steps in the KSYS LPAR:

To discover all the resources across both sites, run the following command:
```
ksysmgr discover site site_name
```
The KSYS subsystem discovers all the hosts and virtual machines from all the host groups across both the sites. Therefore, it might take a few minutes to discover all the hosts and to display the output.
To discover all the hosts in a specific host group, run the following command:
```
ksysmgr discover host_group hg_name
```
To discover all VMs in a specific workgroup, run the following command:
```
ksysmgr discover workgroup workgroup_name
```

Note:

To obtain boot disk information, which is used in multiple boot disk support during the verification and the move operations, the RMC connection of a virtual machine must be in active state.

VM auto-discovery

VM auto-discovery is a system-level property. You can disable or enable this property. By default, this property is enabled.

By default, the KSYS subsystem manages all VMs automatically. The VM auto-discovery property allows the KSYS subsystem to manage or unmanage the newly created VMs and undiscovered VMs.

If the VM auto-discovery property is enabled, all VMs are managed automatically. If the auto-discovery property is disabled, all the newly created VMs on the KSYS managed hosts and the undiscovered VMs (existing VMs that are not yet discovered by the KSYS subsystem) will not be managed by the KSYS subsystem.

To check whether the VM auto-discovery property is enabled or disabled to discover the resources across the site, run the following command:
```
ksysmgr -a vm_auto_discovery query system
```
An output that is similar to the following example is displayed:
```
System-Wide Persistent Attributes
  vm_auto_discovery: enable
```
To enable the VM auto-discovery property, run the following command:
```
ksysmgr modify system vm_auto_discovery=enable
```
To disable the VM auto-discovery property, run the following command:
```
ksysmgr modify system vm_auto_discovery=disable
```