I would like to replace four aging physical servers with one virtual server. What is the best way to insure the VM server is sized correctly? The requirements of the apps that will be running on the four servers are

APPLICATION SERVERS - QTY 3 - These will run the application layer for the web server, Business Objects Business Intelligence app, and various other small client server apps. The three most heavy hitting apps each have the following server requirements. So, if I bought three physical servers, this would be the requirements for each of them Processor - Dual 2.83 GHZ (or faster) Ram - 4 GB Raid 5 - 50-100GB usable space NIC - 1 GB

Web Server - this will run one asp.net e-business app that will talk to our dedicated SQL server and the three app servers above. The E-Business software has these requirements for the web server

Processor - Quad 2.83 GHZ (or faster) Ram - 8 GB Raid 5 - 50-100GB usable space NIC - 1 GB

What is the best tool to determine what I need from a hardware standpoing in a virtual server? I am planning on using VMWare.

  • Which VMWare product will be hosting this? ESXi? – sysadmin1138 Apr 14 '11 at 19:36
  • ESXi was planned, unless we may need to add an essentials pack for more cores – vdubs Apr 14 '11 at 19:39

Monitor the performance of the servers you have now.

Memory and IOPS is the most important to think about. Cpu is rarely an issue.

If you got the money for it try and get a SAN that you can expand on later and 2 Physical servers. This way you can do hardware maintenance on the servers without going offline.

  • Yup, memory will be your main issue and even then you may get away with a lot less than your physical servers have now. When you monitor your servers, make sure you do it during their peak times – xXhRQ8sD2L7Z Apr 14 '11 at 22:15

Vmware Capacity Planner is your best bet. However, you will have to sign up as a partner (easy to do), or have a partner/reseller run it for you. In the end, you will have accurate details about the utilization of your current hardware, as well as a good idea of what you will need.

  • This is truly the best way to size a Virtual Server +1 for the obvious answer – Fergus Apr 15 '11 at 4:36

Without more information about the average load placed on these servers it's going to be hard to give a great answer.

I can tell you that if the load is "average", you can probably get away with running all of these server's on a single ESXi box.

In our production enviornment we have ~45 VM's running accross 4 ESX boxes with no problems what so ever. We could run even more from a CPU usage standpoint. RAM is the first thing that we will run out of. However we are only consuming about 50% right now (each system has 32GB so we have 128GB total).


Instead of trying to size-up a BIG machine to do it, I'd recommend exploiting the fact that you have VMs and can spawn them as and when necessary. So, I'd recommend buying a bunch of smaller machines and distributing your work-load across them.


To fit your environment and avoid creating single points of failure within your your new virtual environment. I would recommend two dual socket 6 core servers with 128G of RAM a couple internal SAS drives in a RAID one to host ESXi and 2 dual 10Gbe interfaces if you plan on using vsphere 4.x or 3 dual 10Gbe interfaces if you plan on using vsphere 5.x. Each server will cost you about $7K US.

For shared storage in a small environment I would recommend two iSCSI arrays with SAS disk. You can pick up a decent 10Gbe copper array for about $10K US. Never use SATA drives in a virtual environment for anything other than disk backup.

For switches I would recommend Arista 7100T. They are easy to setup, cost about $10K US and outperform the other big business switches. If cost is a big option there are several ways to down size this solution to about $15K US.

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