Hello Claire,
The consultants are correct. You should get some form of capacity planning done to determine which Physical systems are the best candidates for virtualization. Actually getting in the hardware before you go down this road may have been putting the cart before the horse, but it is a start. You need to look at the Disk/CPU/Network/Memory Utilization over a period of time for each host and determine if that host can be virtualized or not.
Your limitation on what can be virtualized will be the amount of memory in the Dell machines. You may not have enough to virtualize as many systems as you desire. Take this example: Your Memory Utilization for your servers is 3GBs, if your machines only have 8GBs each, that means you could virtualize up to 2 machines per HOst, or only 4 VMs for the two boxes. Yet if your memory utilization is only 512MBs MAX you could virtualize 15 hosts per system (you need to leave some memory for the vmkernel and SC). But that is just memory, now throw in DIsk IO, Network IO, CPU utilization and you may still not get to where you want. However memory is the biggest hit.
How many NIC Ports/FC-HBA ports on the systems will also make a difference, for full redundancy you want at least 2 FC-HBA, and 6 Physical NIC (pNICs) ports on the machines. If you are running DMZ/Production VMs on the same host (not recommended by the way) you want to have at least 8 pNICs for fully secure, redundancy, and performing systems. Did the consultants do some disk planning on the ESX Servers before installing, or take the default install? If so then you may have too little disk space assigned to the Service Console partitions. Or not enough to do good backups, etc. You need to consider backup requirements with your Virtualization servers as well....
Best regards,
Edward L. Haletky, author of the forthcoming 'VMWare ESX Server in the Enterprise: Planning and Securing Virtualization Servers', publishing January 2008, Copyright 2008 Pearson Education. Available on Rough Cuts at http://safari.informit.com/9780132302074
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Edward L. Haletky
vExpert XIV: 2009-2023,
VMTN Community Moderator
vSphere Upgrade Saga: https://www.astroarch.com/blogs
GitHub Repo: https://github.com/Texiwill
