Virtualization Pro

May 12 2009   1:30PM GMT

Memory usage in vCenter Server 4.0

Eric Siebert Eric Siebert Profile: Eric Siebert

If you are using vCenter Server and plan on upgrading to vSphere you should be aware that vCenter Server 4.0 uses much more memory than vCenter Server 2.5 does. According to the official documentation for both 2.5 and 4.0, the system requirements are very similar:

  • 2.0 GHz or faster Intel or AMD x86 processor. Processor requirements can be more if your database runs on the same hardware.
  • 2 GB RAM. You might need more RAM if your database runs on the same hardware.

But VMware has a note in the vSphere documentation that states:

vCenter Server includes a service called VMware vCenter Management Webservices. This service requires128MB to 1.5GB of additional memory. The vCenter Management Webservices process allocates the required memory at startup.

This Webservices component is a Windows service called VMware VirtualCenter Management Webservices. It’s a Tomcat Java application server that is a component of the vCenter Server. You will see this service listed in Task Manager as tomcat6.exe as vCenter Server 4.0 uses the newer Tomcat 6 version. In vCenter Server 2.5, this service was listed as tomcat5.exe, vCenter Server 2.5 uses the older Tomcat 5.5 version. The Webservices component is not used just for Web browsers to access the vCenter Server, many other services rely on this component. If you stop this service component, vCenter Server will still work but anything that relies on Webservices will no longer work (i.e. plug-ins, Converter).

While the documentation lists equal memory requirements for each version you will find that vCenter Server 2.5 typically uses very little RAM. My tomcat5.exe service on a vCenter Server 2.5 server that manages 6 ESX hosts has been running for weeks and is only using about 50 MB of RAM. The total RAM usage for the host is less than 600 MB.  On my vCenter Server 4.0 that has been running for a few days and manages 2 ESX hosts, tomcat6.exe is using almost 1.2 GB and the total RAM usage is 1.5 GB.

vCenter Server 2.5

vCenter Server 2.5

vCenter Server 4.0

vCenter Server 4.0

So while the memory requirement for both versions of vCenter Server may be equal (2 GB) the actual memory usage between the two versions is not. In version 2.5 you could easily get away with 1 GB, but for version 4.0 you definitely need 2 GB.

2  Comments on this Post

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  • Pelicanintl
    Hi Eric, Thanks for this thoughfull comments. But now the killer question : Can vSphere 4 run on top of tomcat 5 ? if yes, is there a way to avoid the installation / upgrad of the Tomcat Apache server ? In the end, all what vCenter requires is a Webserver... Thanks and have a great time, Beat A VMWare Admin
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  • Michelle Laverick
    The interesting thing about this change - is how 2GB of RAM and 2Ghz of CPU is practically the standard amount that VMWare use for all of the windows products such as SRM and View3. Given that good VM sizing is art that we can all learn - it be nice to see the parent of virtualization (VMware) give us a bit more to go on when we come to size up their own services. I find it an little irrtating that we need this web-service (as opposed to the end-user service). But I guess what with SOAP and XML being the backbone of the SDK it is unavoidable. Roll on vCenter being a download virtual appliance without the need of commerical database... There is one available already. Unfortunately, its only QA'd against Vi3.5 not vSphere4
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