Documenting a virtualization project

Experiences in Virtualization

The budget: get the specs right (2)

Posted by martijnl on June 30, 2006

Advanced Technical Design GuideSo after deciding on the platform it was time to size it to our needs. Based on a quick inventory of our serverpark we estimated 80-100 servers could be virtualized. Based on the sizing guide in the excellent book “ESX Server: Advanced Technical Design Guide” (link to we calculated at 4-6 VM’s per CPU core.

Going the safe route this came out as:

100VM’s / 4 = 25 CPU cores. 25 / 8 (cores per server) = 3,125 servers.

So going the safe route all the way we were budgetting for 4 HP DL585’s. Deciding on the specs of the servers itself was relatively easy after that.

We have had some questions about using Blades but at the moment they are not an option because of the VM density we are running. As described in the VMWare guidelines you need:

  • a seperate NIC for the VirtualCenter management traffic
  • a seperate NIC for VMotion traffic
  • a seperate Gbit NIC for every 4 to 8 VM’s

With roughly 25 VM’s on a host machine that calculates to at least 5 NIC’s in the machine and the first Blades with four NIC’s have only just arrived. If you have the time and the facilities to test it all out it could work for you but as we weren’t using Blades anyway the decision was made pretty quickly to dump that idea.

The serverspecs are described in a seperate page together with some more information about how we arrived at that specific configuration.


2 Responses to “The budget: get the specs right (2)”

  1. Ken said

    The one thing you didn’t mention in your HW specs is storage. In order to take advantage of many of the best features of the VI (HA, DRS, VCB, VMotion) you have to have shared storage.

    Do you plan to use FC, iSCSI, NAS, or what?

  2. martijnl said

    Good point, I will add that in a seperate post. We are currently in an RFI/RFP stage to select a new SAN. Because of our current experience with fiberchannel we will go with FC-SAN again. Manufacturer and definitive solution are not yet decided upon.

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