Top 5 Planet V12n blog posts week 21

You all know the drill by now:

  • Simon Long – Using vMA As Your ESXi Syslog Server
    When vMA collects the logs from your ESXi Host, sometimes the logs have the ESXi Host timestamp and sometimes they will have the vMA Localtime timestamp. I'm not exactly sure why this happens, but it does. (You may or may not know that ESXi uses UTC as its timezone when it timestamps the logs. You can read more about that here. VMware have told me this cannot be changed.)
  • Didier Pironet – The host does not have sufficient memory resources to satisfy the reservation
    I removed the host from the cluster, made a direct connection with vCenter client and booted up the VM, but still same error. I could say that something was wrong with the host only, and not with the VMware cluster’s resource allocation config.
  • Hal Rottenberg – Getting around PowerCLI roadblocks: Tips from the field
    In order to move past this barrier, you have to use the Get-View cmdlet. Get-View is very useful — it's like having a release valve that lets you bust out some really cool tricks. I'm not going to go into great detail about the cmdlet here, but what you need to know is that the PowerCLI cmdlets present an interface to the virtualization administrator which is customized to be consistent with how PowerShell works. This is great for administrators when it works, but when you hit against limits of the included cmdlets, you have to work with the underlying API objects. In other words, you need to understand a totally different interface — the same one that programmers see when they develop software for vSphere.
  • Duncan Epping – Swapping
    As always the common theme of the discussion was “swapping bad”. Although I don’t necessarily disagree. I do want to note that it is important to figure out if the system is actually actively swapping or not. In many cases “bad performance” is blamed on swapping. However this is not always the case. As described in my section on “ESXTOP“ there are multiple metrics on “swap” itself. Only a few of those relate to performance degradation due to swapping. I’ve listed the important metrics below.
  • Frank Denneman – Re: Swapping
    When a virtual machine guest OS starts, there will be a period of time before the VMware tools is loaded and the vmmemctl (balloon driver) is operational. During this timeslot the operating system can access a large portion of its configured memory. Windows systems are notorious for this as they tend to touch every page until it reaches the end of their configured memory. Unfortunately page sharing due to Transparent Page Sharing (TPS) is also at a minimum. Redundant memory pages are not collapsed immediately when a virtual machine is started. TPS is a VMkernel background process and uses a cycle of 60 minutes (Mem.ShareScanTime) to scan a virtual machine for page sharing opportunities.


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