Virtual servers performance question

Dear Experts

I have about 6 ESX boxes running a total of 30 VMs. I am in the process of evelating how to improve performance. ESX specs below:

HP ProLiant DL380 G5
Intel(R) Xeon(R) CPU 5160 @ 3.00GHz
2 processors, 20GB Memory 4 NICs running 5 VM machines

At the moment, CPU utilization is constantly at 82% and memory at 100%

My question is would it be possibe to configure the xen servers on the vm server differently so they can utilize more of the vms processor and memory?  

Who is Participating?
Andrew Hancock (VMware vExpert / EE MVE^2)Connect With a Mentor VMware and Virtualization ConsultantCommented:
Citrix XEN Servers by design and use, naturally use High CPU and Memory. We do not believe that they are ideal candidates for virtualisation, because the Citrix XEN servers perform better when not used under a Hypervisor.

If the Citrix XEN servers were on a Physical Servers, you would get more con-current users per server at the same CPU and Memory utilisation.

You could certainly allocate more memory, but the issue is the CPU bottleneck, so reduce the number of users per Citrix Xen server, and create more Virtual Citrix Xen Servers in the Farm.
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
what do you mean by Xen Servers?

What are the VMs?

Are you trying to improve the performance of the VMs?

Do you have performance issues?

Veeam Monitor for free

If you want a quick tool, to help you with wanting to know all the individual elements, then I would suggest using Veeam Monitor Free Edition

Veeam Monitor leverages Veeam Business View™ to enable performance monitoring, alerting and reporting for virtual machine groups based on criteria such as business unit, department, location, purpose, service-level agreement or any other criteria you define. This ability to perform business-centric monitoring helps to identify the business impact of a virtual infrastructure’s performance and respond accordingly. It also allows you to configure flexible alerts based on known server type characteristics and the potential business impact of an outage for more granular service-level management. You can also create targeted reports showing only the data relevant to specific business units, departments or types of server.
More features


If you want to get down and dirty with the servers, then I would recommend the following documents

Performance Monitoring and Analysis

Guest-based performance monitoring is an inaccurate and unhelpful means of evaluating performance in virtual deployments.  See Guest-based Performance Measurement for more inforamtion.  Monitoring and analysis of VMware ESX Server should be performed with esxtop and VirtualCenter.

esxtop is the tried-and-true means of collecting every performance stat  needed and making it available in a way that is conducive to analysis.  The best source of information on launching esxtop can be found in the Resource Management Guide (page 159).

1. Check and correct CPU utilization: CPU Performance Analysis and Monitoring

2. Identify memory bottlenecks and remove: Memory Performance Analysis and Monitoring

3. Characterize storage performance and correct: Storage Performance Analysis and Monitoring

4. Understand and improve the network utilization profile: Network Performance Analysis and Monitoring

Within each of these articles are techniques for using counters from  VirtualCenter and esxtop.  Information on those counters is provided in

vCenter Performance Counters
esxtop Performance Counters

Also, note that, while useless in collecting performance data, Perfmon  can help with analysis of large esxtop output files.  

Using Perfmon for esxtop-based Performance Analysis
idajagneAuthor Commented:
To clarify the Xen (citrix) servers are the guest VMs and I am trying to improve the virtual machines performance.

Thanks for the information. I will review and get back to you.
idajagneAuthor Commented:
Hanccocka - Thanks for the information and your quick reponse!

I have newer ESX boxes running 8 PRUs compared the current 4PRUs ones running the XEN farm. Do you think moving these XEN boxes to the newer ESX will resolve the performance issue?

Also, each Virtual machine is currently alocated one processor, would adding a secon virtual process make any deifferent give the host has 4 physical processes ( 5 VMs on the host)

Note at peak time I have about 300 connected users spread over 15 virtual machines hosted on 3 ESX boxes each with 4 PRUs.

Your assistance is appreciated.

Andrew Hancock (VMware vExpert / EE MVE^2)Connect With a Mentor VMware and Virtualization ConsultantCommented:
Increase the number of Virtual Machines, reduce the Concurrent load on the VMs.

or switch the Xen Servers to Physical Servers.

Additional Processor, could help, you may get a few more users on the VMs.

The only way you will increase performance, is to redcuce the number of concurrent users per VM.

Try switching the VMs to the 8, and check.

In our testing, Citrix Xen Servers are not ideal candiates for Virtualisation.

We get 75 Concurrent users per Quad Core, Dual Processor Physical Server. Convert to Virtual and we get 15-20.

Performance is severely affected by the hypervisor, the costs do not work out, cost of hypervisor, and additional licenses requires for all the VMs for the farm!
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