vSphere vRAM Usage Test

When VMware released vSphere 5 they also implemented a new licensing model that is based on the amount of virtual RAM (vRAM) that is assigned to virtual machines. vRAM is defined as the memory configured to a virtual machine. vSphere 5 licenses are still sold by the CPU socket, but each license comes with a set vRAM entitlement that varies based on the vSphere 5 edition as shown below:

  • vSphere Standard – 32GB per CPU socket
  • vSphere Enterprise – 64GB per CPU socket
  • vSphere Enterprise Plus – 96GB per CPU socket

If the vRAM license entitlement is exceeded you must purchase another full CPU socket license to increase it. In vSphere 5, there are no limits on the amount of physical memory a host can have; instead, the limits are applied to the amount of vRAM assigned to powered on VMs. VMs that are powered off do not count against the allotment but VMs that are powered on have the full vRAM that is assigned to a VM counted towards the allotment regardless of the amount of vRAM that a guest OS is actually using. This includes all memory used by a VM, both physical host memory and any memory that a VM may be swapping to disk because of memory over-commitment.

This licensing change in vSphere 5 requires that administrators continually micro-manage their vSphere environment by controlling VM sprawl and by enforcing prudent, calculated usage of the memory resources. This test enables these administrators to better manage the vRAM and the vSphere 5 licenses by periodically reporting the vRAM allocation to VMs and their usage.

Note:

This test is applicable to vCenter 5 only.

Target of the test : A VMware vCenter server

Agent deploying the test : An internal agent

Outputs of the test : One set of results the vCenter server being monitored.

Configurable parameters for the test
Parameter Description

Test Period

How often should the test be executed.

Host

The host for which this test is to be configured.

Port

Refers to the port at which the specified host listens to.

VC User and VC Password

To connect to vCenter and extract metrics from it, this test should be configured with the name and password of a user with Administrator or Virtual Machine Administrator privileges to vCenter. However, if, owing to security constraints, you are not able to use the credentials of such users for test configuration, then you can configure this test with the credentials of a user with Read-only rights to vCenter. For this purpose, you can assign the ‘Read-only’ role to a local/domain user to vCenter, and then specify name and password of this user against the VC User and VC Password text boxes. The steps for assigning this role to a user on vCenter have been detailed in the Monitoring VMware Infrastructures chapter

vCenter servers terminate user sessions based on timeout periods. The default timeout period is 30 mins. When you stop an agent, sessions currently in use by the agent will remain open for this timeout period until vCenter times out the session. If the agent is restarted within the timeout period, it will open a new set of sessions. If you want the eG agent to close already existing sessions on vCenter before it opens new sessions, then, instead of the ‘Read-only’ user, you can optionally configure the VC User and VC Password parameters with the credentials of a user with permissions to View and Stop Sessions on vCenter. For this purpose, you can create a special role on vCenter, grant the View and Stop Sessions privilege (prior to vCenter 4.1, this was called the View and Terminate Sessions privilege) to this role, and then assign the new role to a local/domain user to vCenter. The steps for this have been discussed in the Monitoring VMware Infrastructures chapter.

Confirm Password

Confirm the password by retyping it in this text box.

SSL

By default, the vCenter server is SSL-enabled. Accordingly, the SSL flag is set to Yes by default. This indicates that the eG agent will communicate with the vCenter server via HTTPS by default.

Webport

By default, in most virtualized environments, vCenter listens on port 80 (if not SSL-enabeld) or on port 443 (if SSL-enabled) only. This implies that while monitoring vCenter, the eG agent, by default, connects to port 80 or 443, depending upon the SSL-enabled status of vCenter – i.e., if vCenter is not SSL-enabled (i.e., if the SSL flag above is set to No), then the eG agent connects to vCenter using port 80 by default, and if vCenter is SSL-enabled (i.e., if the SSL flag is set to Yes), then the agent-vCenter communication occurs via port 443 by default.  Accordingly, the Webport parameter is set to default by default. 

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 vCenter in your environment listens, so that the eG agent communicates with that port for collecting metrics from vCenter.

Detailed Diagnosis

To make diagnosis more efficient and accurate, the eG Enterprise embeds an optional detailed diagnostic capability. With this capability, the eG agents can be configured to run detailed, more elaborate tests as and when specific problems are detected. To enable the detailed diagnosis capability of this test for a particular server, choose the On option. To disable the capability, click on the Off option.

The option to selectively enable/disable the detailed diagnosis capability will be available only if the following conditions are fulfilled:

  • The eG manager license should allow the detailed diagnosis capability
  • Both the normal and abnormal frequencies configured for the detailed diagnosis measures should not be 0.
Measurements made by the test
Measurement Description Measurement Unit Interpretation

Pooled vRAM capacity

Indicates the amount of vRAM capacity currently available in the license.

GB

The vRAM entitlements of VMware vSphere processor licenses are pooled—that is, aggregated—across all CPU licenses managed by a VMware vCenter instance (or multiple linked VMware vCenter instances) to form a total available vRAM capacity.

VMs powered on

Indicates the number of VMs that are currently powered on.

Number

 

Current vRAM usage

Indicates the amount of vRAM currently utilized by the powered-on VMs.

GB

If the vRAM license entitlement is exceeded or exhausted - i.e., if the value of these measures grow close to the value of the Pooled vRAM capacity measure - it is an indication that you must purchase another full CPU socket license.

To minimize this financial impact, administrators now need to do a much better job of managing their vSphere environments. No longer can they afford to waste resources and over-allocate memory to virtual machines; doing so now has a financial impact. Administrators also have to be very careful that all virtual machines are right-sized and are not allocated more memory than they actually need to support their workloads. They also need to stay on top of VM lifecycles to ensure that un-needed VMs are deleted when they are no longer needed.

vRAM utilization

Indicates the percentage of total vRAM capacity that is currently utilized by the powered on VMs.

Percent

Total VMs

Indicates the total number of VMs using this license.

Number

 

vRAM usage if all VMs were on

Indicates the amount of  vRAM that will be used if all the VMs are powered on.

GB

These metrics help administrators evaluate the vRAM and license requirement of the virtual environment. By understanding how much vRAM would be required to power on and run all VMs, administrators can determine whether or not the current vRAM (pooled) capacity would be sufficient.

If the value of these measures are equal to or higher than the Pooled vRAM capacity measure, it indicates that the total vRAM capacity is not sufficient to support all VMs when powered on. You may hence have to decide what needs to be done to ensure that the virtual environment operates at maximum capacity, but with minimal financial impact:

  • Whether to procure additional vSphere licenses, so that the aggregate vRAM capacity increases, or,
  • Whether to power on only a few VMs at a time, so that the vRAM availability is not badly impacted;

vRAM usage if all VMs were on

Indicates the percentage of the pooled vRAM capacity that will be utilized if all the VMs were powered on.

Percent

vSphere hosts

Indicates the total number of vSphere hosts that are currently using this license.

Number

Use the detailed diagnosis of this measure to know which vSphere/ESX hosts are currently using the license.