Disk Space – Xen Test

This test reports the space usage of every volume group supported by the XenServer host.

Target of the test : A XenServer host

Agent deploying the test : An internal/remote agent

Outputs of the test : One set of results for each volume group on a XenServer host

Configurable parameters for the test

  1. Test period - How often should the test be executed
  2. Host - The host for which the test is to be configured.
  3. XEN user - To enable the eG agent to connect to the XenServer API for collecting statistics of interest, this test should login to the XenServer as a root user. Provide the name of the root user in the XEN USER text box. Root user privileges are mandatory when monitoring a XenServer 5.5 (or below). However, if you are monitoring XenServer 5.6 (or above) and you prefer not to expose the credentials of the root user, then, you have the option of configuring a user with pool-admin privileges as the xen user. If you do not want to expose the credentials of a root/pool-admin user, then you can configure the tests with the credentials of a xen user with Read-only privileges to the XenServer. However, if this is done, then the Xen Uptime test will not run, and the Xen CPU and Xen Memory tests will not be able to report metrics for the control domain descriptor. To avoid such an outcome, do the following before attempting to configure the eG tests with a xen user who has Read-only privileges to the XenServer:

    • Modify the target XenServer’s configuration in the eG Enterprise system. For this, follow the Infrastructure -> Components -> Add/Modify menu sequence, pick Citrix XenServer as the Component type, and click the Modify button corresponding to the target XenServer.
    • In the modify component details page that then appears, make sure that the os is set to Xen and the Mode is set to ssh.
    • Then, in the same page, proceed to provide the User and Password of a user who has the right to connect to the XenServer console via SSH.
    • Then, click the Update button to save the changes.
  4. Once this is done, you can configure the eG tests with the credentials of a xen user with Read-only privileges.   

  5. xen password - The password of the specified xen user needs to be mentioned here.
  6. confirm password - Confirm the xen password by retyping it here.
  7. ssl - By default, the Xen Server is not SSL-enabled. This indicates that by default, the eG agent communicates with the XenServer using HTTP. Accordingly, the ssl flag is set to No by default. If you configure the XenServer to use SSL, then make sure that the SSL flag is set to Yes, so that the eG agent communicates with the XenServer using HTTPS. Note that a default SSL certificate comes bundled with every XenServer installation. If you want the eG agent to use this default certificate for communicating with an SSL-enabled XenServer, then no additional configuration is required. However, if you do not want to use the default certificate, then you can generate a self-signed certificate for use by the XenServer. In such a case, you need to explicitly follow the broad steps given below to enable the eG agent to communicate with the XenServer via HTTPS:

    • Obtain the server-certificate for the XenServer
    • Import the server-certificate into the local certificate store of the eG agent

    For a detailed discussion on each of these steps, refer to the Troubleshooting section of this document.

  8. webport - By default, in most virtualized environments, the XenServer listens on port 80 (if not SSL-enabled) or on port 443 (if SSL-enabled). This implies that while monitoring an SSL-enabled XenServer, the eG agent, by default, connects to port 443 of the server to pull out metrics, and while monitoring a non-SSL-enabled XenServer, the eG agent connects to port 80. Accordingly, the webport parameter is set to 80 or 443 depending upon the status of the ssl flag.  In some environments however, the default ports 80 or 443 might not apply. In such a case, against the webport parameter, you can specify the exact port at which the XenServer in your environment listens so that the eG agent communicates with that port.
Measurements made by the test
Measurement Description Measurement Unit Interpretation

Total physical extents

Indicates the total number of physical extents on this volume group

Number

For the Total descriptor, this measure will report the total number of physical extents across all volume groups on the XenServer host.

Used physical extents

Indicates the number of physical extents allocated to this volume group.

Number

For the Total descriptor, this measure will report the total number of physical extents allocated to all volume groups on the XenServer host.

Free physical extents

Indicates the number of allocated extents that are still unused by this volume group.

Number

For the Total descriptor, this measure will report the total number of unused physical extents in all volume groups on the XenServer host.

Ideally, the value of this measure should be high.

Physical extent size

Indicates the current size of the physical extents in this volume group.

MB

For the Total descriptor, this measure will report the total size of the physical extents in all volume groups on the XenServer host.

 

Disk space in use by VMs

Indicates the space in this volume group that is used by VMs.

GB

For the Total descriptor, this measure will report the total space used across all volume groups on the XenServer host.

A high value indicates excessive utilization of a volume group. If the value of this measure is high for the Total descriptor, it indicates that the usage across volume groups is very high. 

Space available for allocation to new VMs

Indicates the amount of free space on this volume group.

GB

This measure reports the difference between the Total disk capacity measure and the Disk space in use by VMs measure.

Ideally, the value of this measure should be high. A very low value could indicate that one/more vMs are utilizing the allocated disk space excessively. To confirm this, check the value of the Disk space in use by VMs measure; if this value is very high, it indicates that the VMs are eroding disk space.

For the Total descriptor, this measure will report the total disk space that is free across all volume groups, and can be allocated to new VMs.

Usage of allocated space

Indicates the percentage of space allocated from this volume group that is used by VMs.

Percent

A value close to 100% is a cause for concern, as it indicates that one/more VMs are draining the disk space. If the situation persists or aggravates, VMs will experience a severe space crunch, which can bring all VM operations to a halt. To avoid this, you will have to isolate the VMs that are eroding the allocated disk space, clear unnecessary files from the disks of those VMs, and make additional space. Else, you should allocate more space to such VMs.

For the Total descriptor, this measure will report the percentage of the total space allocations from all volume groups that is currently utilized by all VMs on the host. If the Total descriptor of this measure reports a high value, it indicates that the VMs on the host are consuming too much space that is allocated to them. You can then compare the value of this measure across volume groups to know which volume group is being used excessively. 

Usage of disk capacity

Indicates the percentage of the capacity of this volume group that is currently in use.

Percent

Ideally, the value of this measure should be low. A very high value indicates that the volume group is running out of space. Under such circumstances, you may want to check the value of Disk capacity allocated to VMs and the Disk space in use by VMs measures to know what is causing the space erosion – is it due to over-allocation of space to VMs? Or abnormal usage of space by the VMs?

For the Total descriptor, this measure will report the percentage of the total disk capacity across all volume groups that is currently used. If the Total descriptor of this measure reports a high value, it indicates excessive usage of storage space across all volume groups. You can then compare the value of this measure across volume groups to know which volume group is being used excessively.

Total disk capacity

Indicates the total capacity of this volume group.

GB

For the Total descriptor, this measure will report the total disk capacity of the host across all volume groups.

Disk capacity allocated to VMs

Indicates the total disk space in this volume group that has been allocated to all VMs on the host. 

GB

For the Total descriptor, this measure will report the total space that is allocated to all VMs from all volume groups on the host.

Disk capacity available for allocation

Indicates the total disk space in this volume group that is yet to be allocated to VMs.

GB

For the Total descriptor, this measure will report the sum of the space in all volume groups that is still to be allocated to VMs. 

Disk space allocated to VMs

Indicates the percentage of disk space in this volume group that has been allocated to VMs.

Percent

A very high value for this measure indicates that too much disk space has been allocated to the VMs. In such a situation, the host may not have enough disk space for its own operations, and this may cause the host’s performance to deteriorate.

For the Total descriptor, this measure will report the percentage of the total disk space across all volume groups that is allocated to all VMs on the host. If the Total descriptor of this measure reports a high value, it indicates that overall, too much storage space has been allocated to VMs. You can then compare the value of this measure across volume groups to know from which volume group the maximum space has been allocated.   

Usage of allocated space

Indicates the percentage of space allocated from this volume group that has been used by the VMs.

Percent

A high value for this measure indicates excessive usage of a volume group by the VMs. 

For the Total descriptor, this measure will indicate what percentage of the total allocated disk space (across all volume groups) that has been utilized by the VMs.