vSphere Performance Troubleshooting tips

Contents:
- Various troubleshooting tips for vSphere.
- It covers CPU, RAM, Network and Storage.

Source:
- my lab
- VMworld
- feedback from others
- manuals

You can find it here: http://communities.vmware.com/docs/DOC-11742

Hope you find it useful.

VMware vSphere Cluster Size

How many ESX/ESXi hosts do you put in a Cluster?

If there is a need for >8 hosts, then I'd go for 8 hosts per cluster.

Reasons why 8, not 4 or 12 or 16 or 32 hosts:

• Best practice for cluster is to give is same hardware spec with same CPU frequency.
• Eliminates risk of incompatibility
• Complies with Fault Tolerant best practices
• So more than 8 means it’s more difficult/costly to keep them all the same. You need to buy 8 hosts a time, which can be expensive.
  
• Too few hosts result in overhead (the “spare” host)
• Too many hosts are harder to manage (patch, performance troubleshooting, too many VMs per cluster, HW upgrade)
• Some cluster changes in the Advanced Attributes requires cluster to be disable and enable.
• It is harder/longer to do this when there are many hosts
• DRS: 
• 8 hosts give DRS sufficient space to “maneuver”
  
• #VM per host decrease by 4x in >8 host.
• 160 VMs per host if <= 8 hosts in cluster
• 40 VMs per host if > 8 hosts in cluster
• We should avoid being near the limit.
• 40 VM/host is easily reached in Lab Manager or View environment.
• Availability: Able to withstand 1-2 host failures
• A balance between too small (4 hosts) and too large (>12 hosts)
• Allow us to isolate 1 host for VM-troubleshooting purpose
• Upgrading >8 servers at a time is expensive ($$) and complex
• Storage: 8 hosts/LUN à a safe value of 16 paths to a LUN
• Consistent with VMware View
• View 4 cluster is limited to 8 hosts if we use View Composer
  
• 8 is easy number to remember. And a lucky one. And we all know that production needs luck, not just experience :-)

That's for my first posting. I sincerely hope it's useful.