Tuesday, January 12, 2010

vSphere Performance Troubleshooting tips

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

- my lab
- VMworld
- feedback from others
- manuals

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

Hope you find it useful.

Saturday, January 2, 2010

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.