After a few weeks and several reasons (professional and non-professional) I finally restarted writing about my current vSphere replication version 6.0 series. This part 2 focus on some network design options and how they might impact SLAs defined for the Recovery Point Objective (RPO).
- vSphere Replication 6.0 –Part 1: Architecture & features at a glance – vSphere Replication standalone and sample network design
- vSphere Replication 6.0 – Part 2: vSphere Replication performance and SLAs
- vSphere Replication 6.0 – Part 3: Architecture & features at a glance vSphere Replication and vCenter enhanced linked mode
Since I summarized the architecture and components in part 1 I am now going to analyze the effects on the performance based on the network design decisions.
Option 1: “Keep as much traffic as possible within the ESXi”
Result via ESXTOP:
-> With the network configuration to minimize the routing effort I was able to nearly utilize to complete vmnic adapter (ca. 900 Mbit / s)
Option 2: “Having replication traffic routed between vSphere Replication Appliance and the VMkernel port”
Result via ESXTOP:
-> As expected the throughput dropped nearly by 50% to around 440 Mbit / s.
I know that those 2 results are depending on the specific characteristic of my homelab environment. The reason I have written that down was to create an awareness that the network decision has an impact on the replication performance and therefore maybe on the fact if you can meet an SLA or NOT.
Let’s make a short calculation within a small scenario.
RPO – Recovery Point Objective: How much data can get lost during a failure. This value is configured during the setup of a replication job and defines within which time-interval the concrete replication is started
| Amount machines | 15 |
| VM Size | 100 GB = 102400 MB |
| Max average daily disk-change rate | 5% |
| Max Replication transfer rate option 1 | 901 Mbit / s = 112,625 MB / s |
| Max Replication transfer rate option 1 | 440 Mbit / s = 55 MB / s |
The initial replication can be calculated with the following formula:
and will take the following amount of time in our scenario:
Option 1:
Option 2:
To meet a SLA we are in most cases more interested about how long the ongoing replication will take place.
Option 1:
Option 2:
So if you have an RPO defined with 15 minutes there is a risk not to meet the SLA within option 2.
Maybe I repeat myself, but that this is just an example of a calculation (and depending on the use case the limiting factor will be the link between the protected and replicated site). Nevertheless you need to get aware of the following relevant metrics when you design replication:
- replication-throughput
- change-rate
- number and size of your VMs.
In production we don’t want to receive an RPO violation alarm (technically or by the service manager ;-). If you can’t meet the requirements in a theoretical calculation, you will not be able to meet them during daily operations.
Which tool can we use to get the above metrics? Replication-throughput via ESXTOP (network-view: n), number and size of your VMs via PowerCLI (If haven’t done stuff with PowerCLI so far, this is a great starting task for it ;-).
For gathering data about the data change-rate within a VM I refer to a PowerCLI script Scott Herold (his name was in the comments) has created a few years ago that used the change-block-tracking mechanism. I found the script via google and you can download it here (Download: CBT_Tracker – Howto). No need to say that you should understand it (and it’s influence on your system – it uses CBT and snapshots – see the comments within the script) and test the script first before you use it for your analysis.
Compression – The X-Files continues
As I have already said VMware has included a new compression mechanism in 6.0 to speed up the initial copy job. During my first tests (Setup 1 with compression enabled) I had a higher CPU utilization (that’s expected on my vSphere Replication Appliance), but also a lower Throughput of the replication data. I am totally unaware what went wrong here. I will try to figure out more about this effect and keep you informed ;-). If you have any ideas/hints what went wrong in my setup. Please comment or contact via Twitter (@lenzker).
December 20, 2018 at 12:58 pm
Hi guys, it’s Eliot Estes here!
I work as an academic writer and have created this content with the intent of changing your life for the better. I started honing my writing abilities in my school years. I learned that my fellow students needed writing help—and they were willing to pay for it. The money was enough to help pay my tuition for my remaining semesters of college.
Ever since high school, I have continued to work as a professional writer. I was hired by a writing service based in the United Kingdom. Since then, the dissertations that I have created have been sold around Europe and the United States.
In my line of work, I have become familiar with hearing, “Eliot, can you help me meet my writing assignment deadline?” I know that I can provide this service.
Professional Writer – Eliot Estes – Professionalonlineediting Team
December 21, 2018 at 3:18 pm
Hi Everybody
Thanks for checking out my academic writing page . My name is Bentley.
I have worked a long time in this niche. My interest in writing started at a young age. I wrote journaled as a child and eventually went on to work with my school newspaper.
This early tryst into reporting eventually led me to academic writing. There is plenty of work for qualified writers. I specialize in research papers , but have the skills to do all types of academic writing.
Reach out for more information about rates and a price quote. I’m looking forward to helping you.
Academic Writer – Bentley Werner – BibleSkillsInstitute Corp
February 25, 2019 at 6:11 pm
Hey guys, my name is James Oneill!
I`m a professional writer and I`m going to change your lifes onсe and for all
Writing has been my passion since early childhood and now I can`t imagine my life without it.
Most of my books were sold throughout Canada, USA, Old England and even Australia. Also I`m working with services that help people to save their time.
People ask me “Sir, James, I need your professional help” and I always accept the request, `cause I know, that only I can solve all their problems!
Professional Academic Writer – James Oneill – Findingmiddlegroundink-12education Team
March 4, 2019 at 11:17 am
Hey, I am Rima Morrison a professional in academic writing.
I love solving people’s problems and make them happy. That is what I have been doing for decades now.
I have been writing since I was 12 years old and never knew it would turn out to be a full-time career. I have also been able to handle several assignments that involves writing. And I worked in three organizations as a volunteer to assist people.My hobbie has always been to help people succeed. And I go the extra mile to make that happen.
I enjoy writing Thesis and have helped people from countries like UK.
I work with a company whose mission is to provide quality writing and make people happy. In fact, many people come to me for professional help on a daily basis because they know I always deliver. And I will continue to provide nothing but the best to build trust like I have been doing for the past few years.
Expert academic writer – Rima Morrison – Nationaldogguideconference Team
March 18, 2019 at 11:03 am
Hi, my name is Cathy Cornish!
I`m an academic writer and I`m going to change your lifes onсe and for all
Writing has been my passion since early years and now I can`t imagine my life without it.
Most of my poems were sold throughout Canada, USA, China and even India. Also I`m working with services that help people to save their time.
People ask me “Sir, Cathy Cornish, I need your professional help” and I always accept the request, `cause I know, that only I can solve all their problems!
Academic Writer – Cathy Cornish – //www.fredsimpsonwriter.com/]Fredsimpsonwriter Company
March 21, 2019 at 4:52 pm
Hi guys, my name is Brittany Werner!
I`m a professional writer and I`m going to change your lifes onсe and for all
Writing has been my passion since early years and now I cannot imagine my life without it.
Most of my books were sold throughout Canada, USA, China and even Russia. Also I`m working with services that help people to save their nerves.
People ask me “Please, Brittany Werner, I need your professional help” and I always accept the request, `cause I know, that only I can save their time!
Academic Writer – Brittany Werner – Soundacademyrecords Team
March 22, 2019 at 10:01 am
Welcome everyone ! I’m Macie Griffin.
Even though I jokingly credit my mother for my writing talent, I know that it is a skill I have fostered from childhood. Though my aunt is a writer, I also started out young.
I’ve always had a way with words, according to my favorite educator. I was always so excited in science when we had to do a research paper .
Now, I help current students achieve the grades that have always come easily to me. It is my way of giving back to students because I understand the obstacles they must overcome to graduate.
Macie – Academic Writing Professional – Victordematha Company