1.7.5 Monitoring disk resources

This subsection explains how to monitor the disk resources of a KVM system.

Organization of this subsection

(1) Overview
(2) Monitoring examples

(1) Overview

In a KVM system, one of the following methods is used to provide disk resources to a virtual machine:

Allocation to a virtual machine of a virtual hard disk file created on the physical disk
Allocation of a physical disk to a virtual machine

The OS running on a virtual machine recognizes the allocated disk resources as a normal physical disk.

Information on disk resources can be classified as the disk I/O resource (which includes information such as the disk transfer rate) and the disk space resource (which includes information such as the disk capacity). PFM - RM for Virtual Machine provides records for these two types of disk resources. When you monitor a KVM system, you can use the records listed below to monitor the disk resources. Note that the PI_VLDI record that indicates a virtual machine's disk space resource is not supported.

PI_HPDI record

This record is used to monitor the performance data of the physical disk. It shows the disk I/O resource as viewed from the physical server.
PI_VPDI record

This record is used to monitor the performance data of the physical disk being used by a virtual machine. It shows the disk I/O resource as viewed from the virtual machine.
PI_HLDI record

This record is used to monitor the performance data of the physical server's logical disk. It shows the disk space resource as viewed from the physical server.

The following figure shows the range of performance data collected in each record.

Figure 1‒76: Correspondence between records and data collection ranges

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(2) Monitoring examples

This subsection uses an example of monitoring disk 1 and disk 2 installed on the physical server to explain the problems that might occur in disk resources and how to solve them. The following figure shows the items monitored here and the flow of actions to take.

Figure 1‒77: Monitored items and flow of actions

(a) Example of monitoring the space usage of a physical server's logical disk

You can check whether a physical server's logical disk has sufficient free space based on the space usage.

You can check the space usage in the Used % field of the PI_HLDI record. Note that you can monitor this field using an alarm that is provided in the monitoring template. The figure below shows a monitoring example.

Figure 1‒78: Example of monitoring the space usage of a physical server's logical disk

Monitoring template report to be checked: Host Disk Used
Monitoring template alarm to be checked: Host Disk Usage

In this example, the space usage of Disk 2 is high. If the space usage is high, you can solve this problem by expanding the logical disk space through the addition of a physical disk.

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