IPv4 Addresses Cheat Sheet

Bellow is my cheat sheet about IPv4 addresses and subnetting.

The cheat sheet is primarily for myself :-), but somebody else can find it helpful and use it.

Description: The math binary representation of IP octets (bytes) and relation to Net Subnetting.

Keywords: Class Addressing, Classless Addressing

Monolithic versus Microservices application architecture consideration

Microservices application architecture is very popular nowadays, however, it is important to understand that everything has advantages and drawbacks. I absolutely understand advantages of micro-services application architecture, however, there is at least one drawback. Of course, there are more, but let's show at least the potential impact on performance. The performance is about latency.

Monolithic application calls functions (aka procedures) locally within a single compute node memory (RAM). Latency of RAM is approximately 100 ns (0.0001 ms) and Python function call in decent computer has latency ~370 ns (0.00037 ms). Note: You can test Python function latency in your computer with the code available at https://github.com/davidpasek/function-latency/tree/main/python

Microservices application is using remote procedure calls (aka RPC) over network. Typically as REST or gRPC call over https, therefore, it has to traverse the network. Even the latency of modern 25GE Ethernet network is approximately 480 ns (0.00048 ms is still 5x slower than latency of RAM), and RDMA over Converged Ethernet latency can be ~3,000 ns (0.003 ms), the latency of microservice gRPC function call is somewhere between 40 and 300 ms. [source] 

Conclusion

Python local function call latency is ~370 ns. Python remote function call latency is ~280 ms. That's the order of magnitude (10^6) higher latency of micro-services application. RPC in low-level programming languages like C++ can be 10x faster, but it is still 10^5 slower than local Python function call.

I'm not saying that micro-services application is bad. I just recommend to consider this negative impact on performance during your application design and specification of application services.

Grafana - average size of log line

As I'm currently participating on Grafana observability stack Plan & Design exercise, I would like to know what is the average size of log line ingested into the observability stack. Such information is pretty useful for capacity planning and sizing.

Log lines are stored on Loki log database and Loki itself is exposing metrics into Mimir time series database for self monitoring purpose. Grafana Loki and Promtail metrics are documented here.

The following formula calculates average size of log message:

sum(rate(loki_distributor_bytes_received_total [7d])) / sum(rate(loki_distributor_lines_received_total [7d]))

The result is visualized in the screenshot below.

 Hope this tip will be useful for someone else.

Farewell VMware

The clever people and Buddhists know that the only constant thing in the world is change. The change is usually associated with transition, and as we all know, transitions are not easy, but generally good and inevitable things. All transitions are filled with anticipation and potential risks, however, any progress and innovations are only achieved by accepting the risk and going outside of the comfort zone. That's one of the reasons I have decided to leave VMware, even though VMware organization and technologies are very close to my heart, and I truly believe that the VMware software stack is one of the most important IT technology stacks for the future of humans. 

As I prepare to move on, I have to say goodbye and a big thank you to the VMware organization. VMware technologies are part of my daily life for a long time, using the technology since 2006, and I’ll really miss the VMware family I joined back in 2015. It was a great time, and I will especially miss VMware core technical folks transforming the industry and building one of the best software-defined infrastructure stacks humans have done so far. 

And where do I actually go? Back in 2001, I was the co-founder of the software start-up, where I started my professional career by architecting, developing, and operating the air ticket online booking platform, which was later acquired by Galileo Travelport https://www.travelport.com. Now, after 20 years, I have got the proposal to help Kiwi.com to become the # 1 digital system in the modern digitalized travel industry. For those who do not know Kiwi.com, Kiwi.com was originally a Czech start-up growing into a worldwide #3 air ticketing booking platform. They were acquired by General Atlantic back in 2019 https://www.generalatlantic.com/media-article/general-atlantic-announces-strategic-partnership-with-travel-platform-kiwi-com/, and General Atlantic’s past and current investments in the global online travel industry include Priceline, Airbnb, Meituan, Flixbus, Uber, Despegar, Smiles and Mafengwo can tell you where the online travel industry is heading. Those who can read between the lines understand that such a mix allows to build optimal door-to-door traveling for the next human generation(s). I have decided that I would like to be part of such travel industry transformation! Not only because Kiwi.com really does multi-cloud with Kubernetes at a large scale, but mainly to be part of a very young, innovative, and inspiring team including hundreds of software developers and dozens of infrastructure platform and DevOps engineers operating everything as cloud computing.

I'm expecting big fun and you can expect more blog posts about DevOps, multi-cloud, Docker, Kubernetes, CI/CD, Observability, and infrastructure for modern applications because I have to learn and test a lot of new technologies and writing the blog post is the great way to share new knowledge and getting the feedback from other folks in various communities.

Hope my blog will be still useful for my current readers who are typically very IT infrastructure-oriented, however, the software eats the world, and the IT infrastructure is here to support software, isn't it? 

VMware vSphere DRS/DPM and iDRAC IPMI

I have four Dell server R620 in my home lab. I'm running some workloads which have to run 24/7 (DNS/DHCP server, Velocloud SD-WAN gateway, vCenter Server, etc.), however,  there are other workloads just for testing and Proof of Concepts purposes. These workloads are usually powered off. As electricity costs will most probably increase in near future, I realized VMware vSphere DRS/DPS (Distributed Resource Scheduler/Distributed Power Management) could be a great technology to keep the bill of electricity at an acceptable level.

VMware vSphere DPM is using IPMI protocol to manage physical servers. IPMI has to be configured per ESXi server as depicted in the screenshot below.

I have iDRAC Enterprise in my Dell servers and I thought it will be a simple task to configure iDRAC by just entering the iDRAC username, password, IP address, and MAC address.

However, I have realized that the configuration operation fails with an error message "A specified parameter was not correct: ipmiInfo".

During troubleshooting, I tested ipmi (ipmitool -I lanplus -H 192.168.4.222 -U root -P calvin chassis status) from FreeBSD operating system, and I have realized it does not work as well.

That led me to do some further research and to find, that iDRAC doesn't have IPMI enabled by default. iDRAC command to get the IPMI status is "racadm get iDRAC.IPMILan"

iDRAC command "racadm set iDRAC.IPMILan.Enable 1" enables IPMI over LAN and the command "racadm get iDRAC.IPMILan" can be used to validate the IPMI over LAN status.

After such iDRAC configuration, I was able to use IPMI from FreeBSD operating system.

And it worked correctly in VMware vSphere as well as depicted in the screenshot below. 

When IPMI is configured correctly on ESXi, the ESXi host can be switched into Standby Mode manually from vSphere Client as ESXi action.   

The ESXi Standby Mode is used for vSphere DRS/DPM automation. 

Job done!

Hope this helps some other folks in the VMware community.

vSAN Health Service - Network Health - vSAN: MTU check

I have a customer having an issue with vSAN Health Service - Network Health - vSAN: MTU check which was, from time to time, alerting the problem. Normally, the check is green as depicted in the screenshot below.

The same can be checked from CLI via esxcli.

However, my customer was experienced intermittent yellow and red alerts and the only way was to retest the skyline test suite. After retesting, sometimes it switched back to green, sometimes not.

During the problem isolation was identified that the only problem is on vSAN clusters having witness nodes (2-node clusters, stretched clusters). Another indication was that the problem was identified only between vSAN data nodes and vSAN witness. The network communication between data nodes was always ok.

How is this particular vSAN health check work?

It is important to understand, that “vSAN: MTU check (ping with large packet size)”

• is not using “don’t fragment bit” to test end-to-end MTU configuration
• is not using manually reconfigured (decreased) MTU from vSAN witness vmkernel interfaces leveraged in my customer's environment. The check is using static large packet size to understand how the network can handle it.
• The check is sending the large packet between ESXi (vSAN Nodes) and evaluates packet loss based on the following thresholds:
• 0% <-> 32% packet loss => green
• 33%  <-> 66% packet loss => yellow
• 67%  <-> 100% packet loss => red

The vSAN health check is great to understand if there is a network problem (packet loss) between vSAN data nodes. The potential problem can be on ESXi hosts or somewhere in the network path.

So what's the problem?

Let's visualize the environment architecture which is depicted in the drawing below.

The customer has vSAN witness in a remote location and experiencing the problem only between vSAN data nodes and vSAN witness node. Large packet size ping (ping -s 8000) to vSAN witness was tested from ESXi console to test if packet loss is observed there as well.  As we have observed the packet loss, it was the indication, that the problem is somewhere in the middle of the network. Some network routers could be overloaded and do not provide fast enough packet fragmentation causing packet loss.

Feature Request

My customer understands that this is the correct behavior, and everything works as is designed. However, as they have a large number of vSAN clusters, they would highly appreciate, if the check "vSAN: MTU check (ping with large packet size)" would be separated into two independent tests.

• Test #1: “vSAN: MTU check (ping with large packet size) between data nodes”
• Test #2: “vSAN: MTU check (ping with large packet size) between data nodes and witness”

We believe that such functionality would significantly improve the operational experience for large and complex environments.

Hope this explanation helps someone else within the VMware community.

How to get vSAN Health Check state in machine-friendly format

I have a customer with dozens of vSAN clusters managed and monitored by vRealize Operations (aka vROps). vROps has a management pack for vSAN but there are not all features my customer is expecting for day-to-day operations. vSAN has a great feature called vSAN Skyline Health which is essentially a test framework periodically checking the health of vSAN state. Unfortunately, vSAN Skyline Health is not integrated with vROps which might or might not change in the future. Nevertheless, my customer has to operate vSAN infrastructure today, therefore, we are investigating some possibilities for how to develop some custom integration between vSAN Skyline Health and vROps.

The first thing we have to solve is how to get vSAN Skyline Health status in some machine-friendly format. It is well known that vSAN is manageable via esxcli.

Using ESXCLI output

Many ESXCLI commands generate the output you might want to use in your application. You can run esxcli with the --formatter dispatcher option and send the resulting output as input to a custom parser script.

Below are ESXCLI commands to get vSAN HealthCheck status.

esxcli vsan health cluster list
esxcli --formatter=keyvalue vsan health cluster list
esxcli --formatter=xml vsan health cluster list

Option formatter can help us to get the output in machine-friendly formats for automated processing.

If we want to get a detailed Health Check description we can use the following command

esxcli vsan health cluster get -t "vSAN: MTU check (ping with large packet size)"

Option -t contains the name of a particular vSAN HealthCheck test.

Example of one vSAN Health Check:

[root@esx11:~] esxcli vsan health cluster get -t "vSAN: MTU check (ping with large packet size)"

vSAN: MTU check (ping with large packet size) green

Performs a ping test with large packet size from each host to all other hosts.

Ask VMware: http://www.vmware.com/esx/support/askvmware/index.php?eventtype=com.vmware.vsan.health.test.largepin...

Only failed pings

From Host To Host To Device Ping result

--------------------------------------------------------

Ping results

From Host To Host To Device Ping result

----------------------------------------------------------------------

192.168.162.111 192.168.162.114 vmk0 green

192.168.162.111 192.168.162.113 vmk0 green

192.168.162.111 192.168.162.112 vmk0 green

192.168.162.112 192.168.162.111 vmk0 green

192.168.162.112 192.168.162.113 vmk0 green

192.168.162.112 192.168.162.114 vmk0 green

192.168.162.113 192.168.162.114 vmk0 green

192.168.162.113 192.168.162.112 vmk0 green

192.168.162.113 192.168.162.111 vmk0 green

192.168.162.114 192.168.162.111 vmk0 green

192.168.162.114 192.168.162.112 vmk0 green

192.168.162.114 192.168.162.113 vmk0 green

Conclusion

This very quick exercise shows the way how to programmatically get vSAN Skyline Health status via ESXCLI and somehow parse it and leverage vROps REST API to insert these data into vSAN Cluster objects as metrics. There is PowerShell/PowerCLI way how to leverage ESXCLI and do some custom automation, however, it is out of the scope of this blog post.