The Host Side Linking pattern for KVM is designed to establish relationships between:

• Virtual KVM host and any remote storage sources (storage volumes on the SAN system or disk drives on the KVM server);
• Virtual disk drives on the host and the physical storage devices to which they relate.

Below you can see virtual Disk Drive on the KVM virtual host and its connection to the physical devices (Storage Volumes):

How it Work

The Host Side Linking for KVM pattern is triggered when a Red Hat KVM Server Software Instance is detected on a host.
First, the pattern identifies and lists the different virtual machines running on this KVM server, and then parses the list of VMs to collect virtual disks parameters (from the process arguments of the Contributor Process for the SI).

Then, by processing the virtual disks parameters and the information from the actual virtual drives detected on the virtual hosts, the pattern identifies the physical storage devices related to the virtual disk drives.

Note that the KVM Storage pattern does not create local disk drives on the virtual hosts nor links from the file systems to the storage devices. These operations are performed by each OS-related HSL pattern (Linux, Windows, Solaris…).
The Host Side Linking Pattern for KVM creates the following relationships:

• From virtual host to the physical storage device (disk drive or storage volume).

• From the virtual drive to the physical storage device.

The pattern may stop its execution if:

• the pattern was not able to locate a command’s full path (by using “which” system script).

• no software instance(s) for VM(s) running on KVM Server where found.

• some mandatory mappings were not found during the pattern operation.

Prerequisites

Linux Storage and KVM patterns must be uploaded and activated on the BMC Discovery appliance. The KVM Storage pattern is closely dependent on the Linux Storage pattern (the list of commands to run is imported from the Linux Storage pattern).

The Host Side Linking Pattern for KVM launches commands that may require specific execution privileges. The pattern first run commands as the normal user that discovery is using. In case of failure, commands are rerun using PRIV_RUNCMD. In that case, PRIV_RUNCMD will need to be configured to use an appropriate privilege elevation mechanism (see Adding privileged execution to commands for detailed information).

The list of commands that the KVM Storage pattern may run includes:

• lsblk – to get UUIDs for backing devices.

• multipath – to collect multipath information.

• udevadm – to obtain device information and get naa.id for storage volumes.

• udevinfo – to obtain device information.

• hdparm – to obtain device information, if udevadm/udevinfo fails.

• scsi_id – to get naa.id for storage volumes

• pvs – to get the list of physical volumes per volume group.

Note: Depending on the host’s configuration, some commands may remain unused.