How To Guy

How to Monitor vSphere 5 vRAM Pools

• By David Davis
• 11/01/2011

With the introduction of vSphere 5, VMware created the concept of vRAM pools and added this as a critical component of purchasing a vSphere license. While vSphere is still licensed per CPU socket, now each socket license is entitled to a specific amount of vRAM that contributes to a pool.

When vSphere 5 was initially introduced, the announcement of the new vRAM pooled pricing licensing scheme overshadowed the impressive list of new features found in the VMware Cloud Infrastructure Suite. Within three weeks, VMware analyzed customer feedback about vRAM pooled pricing and quickly modified the entitlements (and other aspects) of the vRAM pool calculations to make them more favorable to customers.

Given you can't control how the new vRAM pooled pricing works, the best thing to do is to make sure you understand how to monitor your vRAM pool utilization and know ways to maximize your vRAM pool.

Monitoring vSphere 5 vRAM Pools
Prior to your upgrade to vSphere 5, you'll have the opportunity to use the new vSphere License Advisor. This is a small Windows application that talks to vCenter and calculates your vRAM pool usage—with the new 96GB per virtual machine (VM) max taken into account. It analyzes your current vSphere license count and tells you if you'll be safe or if you'll need more licenses when you upgrade from vSphere 4 to 5.

Once you have vSphere 5 up and running, you may be wondering how it is that you monitor your vRAM pool to ensure you aren't over your entitled limit. You should know that if you use vCenter Standard this is only a “soft limit” and it doesn't prevent you from going over the limit should you need to temporarily power on some VMs.

Monitoring of the vRAM pool is done through the Windows-based vSphere client under Licensing | Reporting. However, the strange thing is, to make the reports available, you must first install the vSphere Web-Client (Server) piece on your vCenter server. In other words, the vSphere Client is actually pulling the reports via the vCenter Web interface. However, even more peculiarly, these reports (today) can't be viewed through the vSphere Web client.

It's still unknown if the released to manufacturing version of vSphere 5 license reporting will incorporate the vSphere 5 license changes made on Aug. 3 that report vRAM pool usage based on a running 12-month-average high-water mark, 96GB per VM cap, and the higher vSphere license vRAM entitlements.

Maximize Your vRAM License Obligation
Regardless of VMware's enhanced generosity with how much vRAM is entitled per vSphere edition, the fact is that you now need to rightsize your VM RAM as accurately as possible. vRAM is now a finite resource with which you need to be frugal.

That being said, what can you do to make the most efficient use of your vRAM? Here are five ways:

• Closely monitor the actual RAM usage of each VM and reduce the amount of configured RAM if possible.
• Power off VMs that aren't in use because, when powered off, they aren't using entitlements from the vRAM pool.
• Understand applications running in each VM to find ways to reduce memory utilizations (if possible).
• Use the same vSphere license across all hosts, because there's a separate pool for each version of vSphere.
• Remember that vCenter servers in linked mode, across multiple locations, can all be combined to contribute to the vRAM pool. Thus, you may have servers at other sites or servers in high availability standby that could all contribute to your vRAM pool.