Interview Questions.

Q1. What Is The Command To Restart /start/prevent Ha Agent In The Esx Host?

Service vmware–aam restart

carrier vmware–aam stop

provider vmware–aam begin

Q2. What Are The Different Types Of Admission Control Policy Available With Vmware Ha?

There are 3 unique types of Admission manipulate coverage to be had.

Host failures cluster tolerates.

Percentage of cluster resources reserved as fail over spare capacity.

Specify a fail over host.

Q3. Explain Does Ha Declare Or Determines That Slave Esxi Has Isolated?

Isolation of ESXi hosts is tested on the basis of heartbeats. The timeline for affirming isolation of slave and grasp ESXi is one of a kind. In this situation we can speak isolation of slave ESXi.

HA triggers a grasp election process before it's going to claim a slave ESXi host is isolated. In this timeline, “s” refers to seconds:

T0 – Isolation of the host (slave)

T10s – Slave enters “election nation”

T25s – Slave elects itself as grasp

T25s – Slave pings “isolation addresses”

T30s – Slave broadcasts itself remoted

T60s – Slave “triggers” isolation reaction

When an ESXi host is isolated, the cost in “electricity on” file is raised to at least one, HA reads this document and validates that ESXi host has been remoted. There is one Power on record consistent with ESXi host and this record carries entries of all the ones VM’s that are currently powered on an ESXi host.

Q4. How To Manually Define The Ha Slot Size?

By default, HA slot length is decided via the Virtual machine Highest CPU and memory reservation. If no reservation is designated at the VM stage, default slot length of 256 MHZ for CPU and 0 MB + memory overhead for RAM might be taken as slot size. We can control the HA slot length manually through the usage of the subsequent values.

There are four alternatives we will configure at HA advanced options associated with slot size

das.SlotMemInMB – Maximum Bound value for HA memory slot length

das.SlotCpuInMHz – Maximum Bound value for HA CPU slot Size

dass.VmMemory inMB – Minimum Bound value for HA reminiscence slot size

dass.VmCpuMin MHz – Minimum Bound price for HA CPU slot length

Q5. What Is Vm Monitoring Status?

HA will typically video display units ESX hosts and reboot the virtual system inside the failed hosts inside the different host within the cluster in case of host isolation but i need the HA to monitors for Virtual gadget screw ups also. Here the characteristic known as VM monitoring status as a part of HA settings.VM tracking restarts the digital device if the vmware equipment heartbeat didn’t received with the desired time using Monitoring sensitivity.

Q6. How Does Ha Keep Track Of Which Vm Are Needed To Be Restart In Case Of An Esxi Host Failure?

When an ESXi host fails, the VM’s which had been strolling on that ESXi are restarted on ultimate nodes within the cluster. But how HA knows that how many VM’s were going for walks on the host before it has failed. The solution is:

HA takes help of 2 documents specifically “energy on” and “Protected listing”. The “strength on file is maintained with the aid of each ESXi host for my part and it includes entries of these VM’s that are currently walking on that ESXi. The “Protected list” document is maintained at datastore stage and tells HA that what have been the VM’s which were blanketed before the failure. On the basis of contents of these 2 documents HA takes decision of restarting VM’s.

When a VM is powered off manually then entry of that VM is removed from “Protected listing” file in order that HA do no longer accidently restart that VM also.

Q7. How The Ha Slots Are Calculated?

I have written a post about how the HA slots are calculated.

Q8. Will Master Election Happen If A New Esxi That Has Visibility To More Datastores Than Existing Master Is Introduced In A Cluster?

No election will now not appear even supposing the newly brought ESXi has visibility to extra datastores than master ESXi host. But in case you reconfigure HA on the cluster then the newly added ESXi becomes grasp due to the fact it's far linked to greater number of datastores.

Q9. Where To Locate Ha Related Logs In Case Of Troubleshooting?

/Var/log/vmware/aam

Q10. What Is Host Isolation?

VMware HA has a mechanism to hit upon a host is remoted from rest of hosts in the cluster. When the ESX host loses its ability to exchange heartbeat via control community between the other hosts in the HA cluster, that ESX host might be considered as a Isolated.

Q11. What Will Happen If The Switch Connected To The Esx Host In Ha Cluster Is Down?

It will not acquire heartbeat and also ping to the isolation deal with additionally failed. So, host will think itself as isolated and HA will provoke the reboot of virtual machines on the host to other hosts in the cluster. Why do you want this unwanted scenario at the same time as acting scheduled protection window.

To keep away from the above state of affairs whilst appearing scheduled hobby which may additionally cause ESX host to isolate, dispose of the test container in ” Enable Host Monitoring” until you are performed with the network upkeep hobby.

Q12. What Will Happen If A Vm Fails When Svmotion Was Going On That Vm And Has Not Been Completed Yet? How This Failure Will Be Handled By Ha?

If a digital machine wishes to be restarted with the aid of HA and the digital device is in the process of being Storage vMotioned and the virtual machine fails, the restart technique isn't began till Vcenter informs the master that the Storage vMotion challenge has completed or has been rolled again.

Q13. What Is Ha Admission Control?

As per “VMware Availability Guide”,

Vcenter Server uses admission control to make certain that enough resources are available in a cluster to offer failover safety and to make certain that virtual machine useful resource reservations are respected.

Q14. What Is Use Of Host Monitoring Status In Ha Cluster?

Let’s take an instance; you are appearing network maintenance interest on your switches which connects your considered one of Th ESX host in HA cluster.

Q15. What Is Slot?

As in keeping with VMware’s Definition,

“A slot is a logical representation of the memory and CPU assets that fulfill the necessities for any powered-on digital system in the cluster.”

If you've got configured reservations at VM degree, It impact the HA slot calculation. Highest reminiscence reservation and maximum CPU reservation of the VM on your cluster determines the slot size for the cluster.

Q16. What Are The Cases When Election Of Master Takes Place In A Cluster?

A master is elected by using a set of HA agents every time the sellers aren't in community contact with a master. A grasp election accordingly takes place whilst HA is first enabled on a cluster and when the host on which the master is strolling:

fails,

turns into network partitioned or remoted,

is disconnected from Vcenter Server,

is positioned into upkeep or standby mode,

or when HA is configured at the host.

Note: Removing slave ESXi from a cluster doesn’t have any effect on election method i.E. If any slave ESXi is eliminated or shutdown or positioned into renovation mode, election will no longer occur.

Q17. What The Maximum Number Is Of Hosts Per Ha Cluster?

Maximum wide variety of hosts in the HA cluster is 32.

Q18. How To Add Additional Isolation Address For Redundancy?

By default, VMWare HA use to ping default gateway because the isolation address if it stops receiving heartbeat. We can upload a further values in case if we're the usage of redundant provider  console both belongs to one of a kind subnet. Let’s say we can add the default gateway of SC1 as first price and gateway of SC2 as the additional one the use of the under value.

Right Click you’re HA cluster

Goto to advanced options of HA

Add the line “das.Isolationaddress1 = 192.168.0.1″

Add the line “das.Isolationaddress2 = 192.168.1.1″ as the extra isolation cope with

Q19. What Is The Different Types Isolation Response Available In Ha?

Power off – All the VMs are powered off, while the HA detects that the community isolation takes place.

Shut down – All VMs going for walks on that host are close down with the assist of VMware Tools, whilst the HA detects that the network isolation happens. If the shutdown thru VMWare gear no longer occurred inside five mins, VM’s strength off operation may be carried out. This conduct can be modified with the help of HA advanced options. Please refer my Post on HA Advanced configuration.

Leave powered on – The VM’s nation remain powered on or remain unchanged, whilst the HA detects that the network isolation takes place.

Q20. If A Slave Esxi Has Been Removed From A Cluster Then Will Election Be Triggered Again?

No removal of slave ESXi from cluster doesn’t has any effect on grasp. No election might be taking place in this situation.

Q21. What Will Happen When Election Of Master Is Going On In A Cluster And At The Same Time One Of The Slaves Esxi Host Also Failed? How This Failure Will Be Handled Since At The Time Of Failure There Is N

It is obligatory that for restarting VM’s master should be present in cluster. Now whilst election is going on in a cluster, it takes 15 seconds to finish the election method. Now for the duration of that point if a slave ESXi additionally fails then restart of VM has to attend until election technique is completed.

The newly elected grasp will first study the “Protected List” record to discover the VM’s whose energy state has been changed. After studying that document it will decide that what number of vm’s have been there which failed at some stage in election time after which will carry out restart of these VM’s.

Q22. How The Host Failures Cluster Tolerates Admission Control Policy Works?

Select the maximum number of host disasters that you may afford for or to guarantee fail over. Prior vSphere 4.1, Minimum is 1 and the most is four.

In the Host Failures cluster tolerates admission manage coverage, we are able to define the particular quantity of hosts that may fail  inside the cluster and also it ensures that the sufficient sources stay to fail over all the digital machines from that failed hosts to the alternative hosts in cluster. VMware High Availability (HA) uses a mechanism referred to as slots to calculate each the available and required sources within the cluster for a failing over virtual machines from a failed host to other hosts in the cluster.

Q23. Explain The Vm Restart Retries Timeline?

HA will reply whilst the country of a number has changed, or while the nation of one or greater digital machines has changed. There are a couple of situations wherein HA will try to restart a virtual device of which we have indexed the maximum common beneath:

Failed host

Isolated host

Failed visitor Operating System

Prior to vSphere five, the real number of restart tries become 6, as it excluded the initial attempt. With vSphere five.Zero the default is @There are particular times associated with every of those attempts. The following bullet list will make clear this idea. The ‘m’ stands for “mins” in this listing.

T0 – Initial Restart

T2m – Restart retry 1

T6m – Restart retry 2

T14m – Restart retry three

T30m – Restart retry four

In case of a host failure, HA will try to restart the digital machine on different hosts in the affected cluster; while appearing the restart if that is unsuccessful on that host, the restart be counted can be elevated with the aid of 1.

Let’s say first restart attempt is made at T0 minutes when the host failure has occurred (In actual restart is not achieved as soon as host has failed due to the fact HA takes a while before putting forward host failure; examine above the 2 situations which I actually have referred to).

If the primary restart strive is failed, then the restart counter is increased through one and the subsequent restart is attempted after 2 minutes (T2). In the equal fashion HA maintain trying restarting the VM until issued electricity on strive is mentioned as “finished”.

A a hit restart might never arise if the restart remember is reached and all five restart attempts were unsuccessful.

Q24. Explain Does Ha Declare Or Determines That Master Esxi Has Isolated?

In the case of the isolation of a grasp, this timeline is a chunk much less complex due to the fact there is no need to go through an election procedure. In this timeline, “s” refers to seconds.

T0 – Isolation of the host (grasp).

T0 – Master pings “isolation addresses”.

T5s – Master declares itself isolated and “triggers” isolation reaction.

Q25. What Is Aam In Ha?

AAM is the Legato automatic availability control.  Prior to vSphere 4.1, VMware HA is simply re engineered to work with VM’s with the help of Legato’s Automated Availability Manager (AAM) software. VMware’s Vcenter agent (vpxa) interfaces with the VMware HA agent which acts as an intermediary to the AAM software program. From vSphere five.Zero, it uses an agent referred to as “FDM” (Fault Domain Manager).

Q26. What Are Prerequisites For Ha To Work?

Shared storage for the VMs strolling in HA cluster.

Essentials plus, widespread, Advanced, Enterprise and Enterprise Plus Licensing.

Create VM HA enabled Cluster.

Management community redundancy to keep away from frequent isolation reaction in case of brief network troubles (favored no longer a requirement).

Q27. How Host Isolation Is Detected?

In HA cluster, ESX hosts uses heartbeats to talk among different hosts inside the cluster. By default, Heartbeat will be despatched every 1 2d.

If a ESX host inside the cluster did now not obtain heartbeat for 13 seconds from any other hosts within the cluster, The host taken into consideration it as remoted and host will ping the configured isolation cope with (default gateway by means of default). If the ping fails, VMware HA will execute the Host isolation reaction.

Q28. Is Admission Control Policy Is Dependent On Vcenter Server And Will Admission Control Policy Will Work If Your Vcenter Is Not Available?

Yes admission manipulate policy is depending on Vcenter Server even though it is a part of HA and we all recognize HA works independently of Vcenter Server. Admission control rules don’t work when at the time of failure of an ESXi host, Vcenter server isn't always to be had. This doesn’t mean VM that had been strolling on failed host will now not be restarted, but anything policy you have chosen that policy will not paintings.

For E.G.:  You have chosen “Specify failover host” coverage and dedicated one ESXi host for handling the failover. Now in regular scenario, if a host failure has took place then HA will failover the failed VM’s on handiest this committed host and no longer on any other hosts in cluster. But if Vcenter isn't to be had and this happens then HA may restarts your VM’s on different hosts additionally if there aren't enough assets available to your certain failover host.

Q29. What Is Maximum Number Of Primary Ha Hosts In Vsphere 4.1?

Maximum wide variety of primary HA host is @VMware HA cluster chooses the first 5 hosts that join the cluster as primary nodes and all others hosts are mechanically selected as secondary nodes.

Q30. What Is Vmware Ha?

As per VMware Definition:

VMware® High Availability (HA) provides clean to use, value effective excessive availability for programs running in virtual machines. In the occasion of server failure, affected virtual machines are robotically restarted on different manufacturing servers with spare ability.

Q31. What Are The 2 Types Of Settings Available For Admission Control?

Enable: Do not electricity on VMs that violate availability constraints.

Disable: Power on VMs that violate availability constraints.

Q32. Which Parameter Need To Configure To Increase The Response Time For Isolation Detection?

You can configure a parameter called “das.IsolationShutdown.Timeout”. The cost of this parameter is laid out in minutes and it is time so that you can be taken by using HA to gracefully shutdown a VM while isolation reaction is set to “Shutdown VM” and it is precipitated.

Q33. What The Basic Troubleshooting Steps In Case Of Ha Agent Installs Failed On Hosts In Ha Cluster?

Below steps are taken from my weblog posts troubleshooting HA:

Check for some network troubles

Check the DNS is configured properly

Check the vmware HA agent popularity in ESX host by way of the use of below commands carrier vmware–aam reputation

Check the networks are nicely configured  and named exactly as different hosts in the cluster. Otherwise, you will get the under mistakes at the same time as putting in or reconfiguring HA agent.

Check HA associated ports are open in firewall to permit for the verbal exchange

Incoming port: TCP/UDP 8042-8045

Outgoing port: TCP/UDP 2050-2250

First try and restart /stop/start the vmware HA agent on the affected host the use of the below commands. In addition u can also try and restart vpxa and management agent inside the Host.

Provider vmware–aam restart

provider vmware–aam prevent

carrier vmware–aam start

Right Click the affected host and click on “Reconfigure for VMWare HA” to re-deploy the HA agent that precise host.

Remove the affected host from the cluster. Removing ESX host from the cluster will not be allowed untill that host is positioned into preservation mode.

Alternative answer for three step is, Goto cluster settings and uncheck the vmware HA in to turnoff the HA in that cluster and re-allow the vmware HA to get the agent established.

For similarly troubleshooting , evaluate the HA logs underneath /Var/log/vmware/aam directory.

Q34. How Does Ha Determines That Esxi Host Is Network Partitioned?

There is a mild distinction among ESXi host isolation and network partitioned. When multiple slave ESXi hosts has remoted together however they can ping every apart from this circumstance is called community partitioned.

For e.G.: Subnet mask of five ESXi has been modified then they'll be not able to speak to master (being on distinct subnets) but they are able to speak to every different (being on equal subnet).

When network partitioned happens in a cluster then election takes place among the isolated slaves ESXi and a new master is elected among them. In this situation there may be 2 masters in a cluster.