Posts

Showing posts from September, 2016

Trending Topics

VMware on AWS - How to restore NSX DFW firewall rules to previous state

Image
Customers who uses NSX day-in, day-out would like to have a point-in time restore functionality of DFW firewall rules. Many customer have a large footprints in VMC and make changes to DFW quite often. This feature was missing for long time and we could see its included in recent versions . Let's see how DFW configuration roll back works  NSX DFW configuration has versioning, and it is stored in the NSX Manager.  Every time when someone update DFW configuration, NSX creates one more version but keep storing the previous ones. You can rollback for previous config but reapplying it once again.  You can find the options under Networking & Security tab , > Security > Distributed Firewall . In the right side we see an Actions drop down. Choose View to get to the below screen.  Let’s go through the use case:  1. Original state- default config with no custom rules:  a. There are no saved configurations during last 30 days: In my existing test setup, with the current setting
Read more

What is the difference between PCPU Used and PCPU Utilized?

I’m often asked the question when looking at vSphere statistics – “What is the difference between PCPU Used and PCPU Utilized and why don’t they match?” Let’s take a look as it can be somewhat complex. First lets start with some definitions: Time Stamp Counter (or TSC) – is a 64 bit register available on all modern processors that counts clock cycles at a consistent rate and is not affected by changes in clock frequency. Unhalted Cycles – another count of ‘all’ clock cycles, but this one is dependent on the clock frequency and therefore the rate can change if the clock frequency changes (due to things like power management or Hyper-Threading). Wall Clock Time – refers to elapsed real world time. Okay now lets define our two counters using the above definitions: PCPU utilized (which is TSC based) = (non-idle state TSC cycles)/wall clock time PCPU used (which is unhalted cycle based) = (unhalted cycles)/wall clock time So assuming a non Hyper-Threaded system, and no pow
Read more