Interview Questions.

Question 1. What Is Vmware Ha?

Answer :

As consistent with VMware Definition:

VMware® High Availability (HA) provides easy to apply, cost effective high availability for programs walking in virtual machines. In the event of server failure, affected digital machines are routinely restarted on other production servers with spare capacity.

Question 2. What Is Aam In Ha?

Answer :

AAM is the Legato computerized availability control.  Prior to vSphere 4.1, VMware HA is actually re engineered to work with VM’s with the assist of Legato’s Automated Availability Manager (AAM) software program. 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 known as “FDM” (Fault Domain Manager).

VMware Infrastructure with ESX Server and VirtualCenter Interview Questions
Question 3. What Are Prerequisites For Ha To Work?

Answer :

Shared garage for the VMs strolling in HA cluster.
Essentials plus, standard, Advanced, Enterprise and Enterprise Plus Licensing.
Create VM HA enabled Cluster.
Management community redundancy to avoid frequent isolation response in case of transient network issues (preferred not a requirement).
Question 4. What Is Maximum Number Of Primary Ha Hosts In Vsphere four.1?

Answer :

Maximum number of primary HA host is 5. VMware HA cluster chooses the first five hosts that be a part of the cluster as number one nodes and all others hosts are robotically selected as secondary nodes.

Question 5. What Is The Command To Restart /begin/stop Ha Agent In The Esx Host?

Answer :

provider vmware–aam restart

carrier vmware–aam stop

carrier vmware–aam start

VMware ESXi Interview Questions
Question 6. Where To Locate Ha Related Logs In Case Of Troubleshooting?

Answer :

/Var/log/vmware/aam

Question 7. What The Basic Troubleshooting Steps In Case Of Ha Agent Installs Failed On Hosts In Ha Cluster?

Answer :

Below steps are taken from my weblog posts troubleshooting HA:

Check for some network issues
Check the DNS is configured properly
Check the vmware HA agent popularity in ESX host via the usage of beneath commands provider vmware–aam popularity
Check the networks are properly configured  and named precisely as different hosts within the cluster. Otherwise, you'll get the beneath errors whilst installing or reconfiguring HA agent.
Check HA related ports are open in firewall to permit for the communique
Incoming port: TCP/UDP 8042-8045
Outgoing port: TCP/UDP 2050-2250
First try and restart /forestall/begin the vmware HA agent at the affected host using the underneath commands. In addition u also can attempt to restart vpxa and control agent in the Host.
Carrier vmware–aam restart
service vmware–aam forestall
provider vmware–aam start
Right Click the affected host and click on on “Reconfigure for VMWare HA” to re-deploy the HA agent that unique host.
Remove the affected host from the cluster. Removing ESX host from the cluster will no longer be allowed untill that host is placed into renovation mode.
Alternative answer for 3 step is, Goto cluster settings and uncheck the vmware HA in to turnoff the HA in that cluster and re-enable the vmware HA to get the agent established.
For further troubleshooting , evaluate the HA logs below /Var/log/vmware/aam directory.
Windows Vmware Interview Questions
Question 8. What The Maximum Number Is Of Hosts Per Ha Cluster?

Answer :

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

Question nine. What Is Host Isolation?

Answer :

VMware HA has a mechanism to detect a host is isolated from rest of hosts within the cluster. When the ESX host loses its capacity to change heartbeat via control community between the other hosts inside the HA cluster, that ESX host will be taken into consideration as a Isolated.

VMware NSX Interview Questions
Question 10. How Host Isolation Is Detected?

Answer :

In HA cluster, ESX hosts uses heartbeats to communicate among other hosts inside the cluster. By default, Heartbeat could be sent every 1 2d.

If a ESX host inside the cluster did no longer get hold of heartbeat for thirteen seconds from some other hosts in the cluster, The host taken into consideration it as isolated and host will ping the configured isolation deal with (default gateway with the aid of default). If the ping fails, VMware HA will execute the Host isolation response.

Question 11. What Is The Different Types Isolation Response Available In Ha?

Answer :

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

Shut down – All VMs strolling on that host are shut down with the assist of VMware Tools, while the HA detects that the network isolation takes place. If the shutdown through VMWare equipment not took place inside five mins, VM’s power off operation will be carried out. This conduct may be modified with the assist of HA superior options. Please refer my Post on HA Advanced configuration.

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

VMware Interview Questions
Question 12. How To Add Additional Isolation Address For Redundancy?

Answer :

By default, VMWare HA use to ping default gateway because the isolation address if it stops receiving heartbeat. We can upload an additional values in case if we are using redundant carrier  console each belongs to one-of-a-kind subnet. Let’s say we will upload the default gateway of SC1 as first cost and gateway of SC2 as the extra one the use of the below value.

Right Click you’re HA cluster
Goto to advanced alternatives of HA
Add the line “das.Isolationaddress1 = 192.168.Zero.1″
Add the road “das.Isolationaddress2 = 192.168.1.1″ as the additional isolation deal with
VMware Infrastructure with ESX Server and VirtualCenter Interview Questions
Question 13. What Is Ha Admission Control?

Answer :

As in line with “VMware Availability Guide”,

Vcenter Server makes use of admission manage to make certain that enough assets are available in a cluster to offer failover protection and to make certain that virtual device aid reservations are reputable.

Question 14. What Are The 2 Types Of Settings Available For Admission Control?

Answer :

Enable: Do now not strength on VMs that violate availability constraints.

Disable: Power on VMs that violate availability constraints.

Question 15. What Are The Different Types Of Admission Control Policy Available With Vmware Ha?

Answer :

There are three distinctive forms of Admission manipulate policy available.

Host disasters cluster tolerates.
Percentage of cluster sources reserved as fail over spare potential.
Specify a fail over host.
Vmware Vsphere Interview Questions
Question 16. How The Host Failures Cluster Tolerates Admission Control Policy Works?

Answer :

Select the most variety of host disasters that you may come up with the money for for or to assure fail over. Prior vSphere 4.1, Minimum is 1 and the most is 4.

In the Host Failures cluster tolerates admission control coverage, we will outline the specific quantity of hosts which can fail  in the cluster and also it guarantees that the sufficient assets stay to fail over all of the virtual machines from that failed hosts to the alternative hosts in cluster. VMware High Availability (HA) makes use of a mechanism referred to as slots to calculate each the to be had and required resources inside the cluster for a failing over virtual machines from a failed host to other hosts within the cluster.

Question 17. What Is Slot?

Answer :

As consistent with VMware’s Definition,

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

If you've got configured reservations at VM stage, It affect the HA slot calculation. Highest memory reservation and highest CPU reservation of the VM for your cluster determines the slot length for the cluster.

Vmware Horizon Interview Questions
Question 18. How The Ha Slots Are Calculated?

Answer :

I actually have written a publish approximately how the HA slots are calculated.

VMware ESXi Interview Questions
Question 19. What Is Use Of Host Monitoring Status In Ha Cluster?

Answer :

Let’s take an instance; you are acting network preservation interest to your switches which connects your one of Th ESX host in HA cluster.

Question 20. What Will Happen If The Switch Connected To The Esx Host In Ha Cluster Is Down?

Answer :

It will now not get hold of heartbeat and also ping to the isolation deal with also failed. So, host will assume itself as isolated and HA will initiate the reboot of virtual machines on the host to other hosts within the cluster. Why do you want this unwanted state of affairs while appearing scheduled protection window.

To avoid the above scenario when appearing scheduled activity which may also reason ESX host to isolate, cast off the take a look at container in ” Enable Host Monitoring” until you're finished with the community protection interest.

VMware DRS Interview Questions
Question 21. How To Manually Define The Ha Slot Size?

Answer :

By default, HA slot length is decided by means of the Virtual device Highest CPU and reminiscence reservation. If no reservation is distinctive at the VM stage, default slot size of 256 MHZ for CPU and 0 MB + memory overhead for RAM may be taken as slot length. We can control the HA slot length manually through the use of the following values.

There are 4 alternatives we can configure at HA advanced options associated with slot length

das.SlotMemInMB – Maximum Bound value for HA memory slot size
das.SlotCpuInMHz – Maximum Bound price for HA CPU slot Size
dass.VmMemory inMB – Minimum Bound fee for HA memory slot length
dass.VmCpuMin MHz – Minimum Bound value for HA CPU slot length
Question 22. How The “percent Of Cluster Resources Reserved As Failover Spare Capacity” Admission Control Policy Works?

Answer :

In the Percentage of cluster assets reserved as failover spare capacity admission control coverage, We can define the specific percentage of total cluster assets are reserved for failover.In assessment to the “Host Failures cluster tolerates admission manipulate policy”, It will no longer use slots. Instead This coverage calculates the inside the way beneath.

It calculates the Total aid requirement for all Powered-on Virtual Machines inside the cluster  and also calculates the total useful resource to be had in host for virtual machines.
It calculates the current CPU and Memory Failover potential for the capability.
If the modern-day CPU and Memory Failover ability for the cluster < configured failover ability (ex 25 %)
Admission control will no longer permit to electricity on the digital system which violates the supply constraints.
Question 23. How The “specify A Failover Host” Admission Control Policy Works?

Answer :

In the Specify a failover host” admission manipulate policy, We can define a specific host as a dedicated failover host. When isolation reaction is detected, HA tries to restart the digital machines on the desired failover host. In this Approach, devoted failover hits will be sitting idle with out actively involving or no longer participating in DRS load balancing.DRS will no longer migrate or power on placement of virtual machines at the defined failover host.

Question 24. What Is Vm Monitoring Status?

Answer :

HA will generally video display units ESX hosts and reboot the virtual device within the failed hosts in the other host inside the cluster in case of host isolation however i need the HA to monitors for Virtual gadget screw ups also. Here the function referred to as VM tracking reputation as part of HA settings.VM monitoring restarts the digital system if the vmware gear heartbeat didn’t obtained with the specified time the usage of Monitoring sensitivity.

Windows Vmware Interview Questions
Question 25. Explain How Restart Of Vm’s Is Handled By Ha In Case Of A Master Esxi Host Failure?

Answer :

HA restarts VM’s after failure of an ESXi host. But the time taken by means of HA to restart VM’s is extraordinary in case of a slave ESXi failure and master ESXi failure. We will talk here the case whilst grasp ESXi has failed.

In case of a failure of a grasp ESXi, restart of VM’s are delayed till the time a brand new grasp is elected because best a grasp can carry out VM restart.

The timeline is defined as follows:

T0 – Master failure.
T10s – Master election system initiated.
T25s – New grasp elected and reads the covered list.
T35s – New master initiates restarts for all virtual machines on the covered listing which are not strolling.
At T0 seconds grasp ESXi has failed, the election procedure is initiated by slave ESXi hosts after 10 seconds at T10. At T25 the newly elected grasp first reads the covered list document to find out which VM had been covered through HA and are presently now not running.  At T35 seconds the grasp ESXi initiates the VM restart.

Question 26. Explain How Restart Of Vm’s Is Handled By Ha In Case Of A Slave Esxi Host Failure?

Answer :

There are  distinct situations for restarting VM’s in case of slave Esxi failure: one wherein heartbeat datastores are configured and one wherein heartbeat datastores are not configured.

The timeline is as follows:

T0 – Slave failure
T3s – Master starts monitoring datastore heartbeats for 15 seconds.
T10s – The host is declared unreachable and the master will ping the control community of the failed host. This is a continuous ping for five seconds.
T15s – If no heartbeat datastores are configured, the host will be declared dead.
T18s – If heartbeat datastores are configured, the host may be declared useless.
The master video display units the network heartbeats of a slave. When the slave fails, those heartbeats will not be received via the grasp. We have described this as T0. After three seconds (T3s), the master will begin tracking for datastore heartbeats and it will do that for 15 seconds. On the 10th 2d (T10s), when no network or datastore heartbeats were detected, the host will be declared as “unreachable”.
The grasp may even start pinging the management network of the failed host on the 10th 2nd and it's going to achieve this for five seconds. If no heartbeat datastores have been configured, the host can be declared “dead” at the fifteenth 2nd (T15s) and VM restarts may be initiated via the master.
If heartbeat datastores had been configured, the host can be declared lifeless on the 18th second (T18s) and restarts can be initiated.
Question 27. Explain The Vm Restart Retries Timeline?

Answer :

HA will respond when the state of a host has modified, or when the nation of one or more virtual machines has changed. There are a couple of eventualities in which HA will try and restart a digital system of which we've got listed the maximum commonplace underneath:

Failed host
Isolated host
Failed guest Operating System
Prior to vSphere 5, the real quantity of restart tries became 6, because it excluded the initial attempt. With vSphere 5.Zero the default is 5. There are particular instances associated with each of those attempts. The following bullet listing will clarify this idea. The ‘m’ stands for “mins” on 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 attempt to restart the digital system on different hosts inside the affected cluster; at the same time as performing the restart if that is unsuccessful on that host, the restart count number could be elevated through 1.

Let’s say first restart attempt is made at T0 mins while the host failure has occurred (In actual restart isn't always achieved as soon as host has failed due to the fact HA takes some time before putting forward host failure; read above the 2 eventualities which I have stated).

If the first restart try is failed, then the restart counter is improved via one and the next restart is attempted after 2 minutes (T2). In the equal fashion HA preserve attempting restarting the VM till issued strength on attempt is pronounced as “finished”.

A a success restart may in no way arise if the restart remember is reached and all five restart attempts were unsuccessful.

VMware NSX Interview Questions
Question 28. Explain Does Ha Declare Or Determines That Slave Esxi Has Isolated?

Answer :

Isolation of ESXi hosts is validated on the basis of heartbeats. The timeline for affirming isolation of slave and master ESXi is distinct. In this case we are able to talk isolation of slave ESXi.

HA triggers a grasp election system before it will declare a slave ESXi host is remoted. In this timeline, “s” refers to seconds:

T0 – Isolation of the host (slave)
T10s – Slave enters “election state”
T25s – Slave elects itself as master
T25s – Slave pings “isolation addresses”
T30s – Slave proclaims itself remoted
T60s – Slave “triggers” isolation response
When an ESXi host is isolated, the value in “energy on” file is raised to 1, HA reads this file and validates that ESXi host has been isolated. There is one Power on report consistent with ESXi host and this file contains entries of all those VM’s that are presently powered on an ESXi host.

Question 29. Explain Does Ha Declare Or Determines That Master Esxi Has Isolated?

Answer :

In the case of the isolation of a master, this timeline is a bit much less complicated due to the fact there's no need to go through an election system. In this timeline, “s” refers to seconds.

T0 – Isolation of the host (master).
T0 – Master pings “isolation addresses”.
T5s – Master pronounces itself isolated and “triggers” isolation reaction.
Question 30. Is Admission Control Policy Is Dependent On Vcenter Server And Will Admission Control Policy Will Work If Your Vcenter Is Not Available?

Answer :

Yes admission control coverage is depending on Vcenter Server although it is part of HA and we all know HA works independently of Vcenter Server. Admission manipulate policies don’t work while at the time of failure of an ESXi host, Vcenter server is not available. This doesn’t suggest VM that have been walking on failed host will now not be restarted, but something coverage you have got selected that policy will no longer paintings.

For E.G.:  You have selected “Specify failover host” coverage and committed one ESXi host for managing the failover. Now in regular state of affairs, if a bunch failure has befell then HA will failover the failed VM’s on most effective this dedicated host and no longer on another hosts in cluster. But if Vcenter isn't always available and this occurs then HA might restarts your VM’s on different hosts also if there are not enough sources available on your distinct failover host.

Question 31. How Does Ha Determines That Esxi Host Is Network Partitioned?

Answer :

There is a mild distinction among ESXi host isolation and network partitioned. When more than one slave ESXi hosts has remoted collectively but they are able to ping every aside from this condition is known as network partitioned.

For e.G.: Subnet masks of 5 ESXi has been modified then they will be not able to speak to grasp (being on specific subnets) however they are able to communicate to each other (being on equal subnet).

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

Question 32. How Does Ha Determines Which Vm’s It Need To Restart Which Were Powered Off Or Shutdown Due To Triggered Isolation Response?

Answer :

If isolation reaction is set to “shut down” or “energy off’ then while an ESXi host is isolated, VM’s are powered off or shutdown because of trigger of isolation reaction. Now the question is how HA preserve tracks of which VM have been powered off/shutdown because of this trigger.

The solution to this query is as follows: When a VM is shutdown/powered off because of triggering of isolation reaction than the host that has remoted do away with entries of these VM’s from electricity on file and creates a consistent with digital system file internal a listing known as “powered off”. HA reads those files to discover the kingdom trade of the VM’s and primarily based on that it takes selection to restart the ones VM’s.

This is vital because, assume while a bunch is isolated and on the same time if a person has manually issued a shutdown/powered off command to a VM, then HA will no longer restart that VM. There can be no file created for that VM by remoted host because it has been manually shut down.

Question 33. How Does Ha Keep Track Of Which Vm Are Needed To Be Restart In Case Of An Esxi Host Failure?

Answer :

When an ESXi host fails, the VM’s which have been going for walks on that ESXi are restarted on last nodes inside the cluster. But how HA knows that how many VM’s have been jogging on the host earlier than it has failed. The answer is:

HA takes help of two files namely “strength on” and “Protected list”. The “power on report is maintained through every ESXi host personally and it includes entries of those VM’s which might be presently going for walks on that ESXi. The “Protected list” record is maintained at datastore level and tells HA that what have been the VM’s which have been covered earlier than 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 list” record so that HA do no longer accidently restart that VM additionally.

VMware Interview Questions
Question 34. Which Parameter Need To Configure To Increase The Response Time For Isolation Detection?

Answer :

You can configure a parameter known as “das.IsolationShutdown.Timeout”. The cost of this parameter is specified in mins and it's time so that it will be taken by using HA to gracefully shutdown a VM when isolation reaction is set to “Shutdown VM” and it is triggered.

Question 35. What Are The Cases When Election Of Master Takes Place In A Cluster?

Answer :

A master is elected via a fixed of HA marketers every time the retailers aren't in network contact with a master. A master election for that reason happens whilst HA is first enabled on a cluster and when the host on which the grasp is walking:

fails,
turns into network partitioned or remoted,
is disconnected from Vcenter Server,
is placed into renovation or standby mode,
or while HA is configured at the host.
Note: Removing slave ESXi from a cluster doesn’t have any impact on election method i.E. If any slave ESXi is removed or shutdown or positioned into preservation mode, election will now not happen.

Question 36. 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 No Master Esxi Host?

Answer :

It is mandatory that for restarting VM’s grasp need to be found in cluster. Now when election is occurring in a cluster, it takes 15 seconds to complete the election manner. Now throughout that point if a slave ESXi additionally fails then restart of VM has to attend till election procedure is finished.

The newly elected master will first study the “Protected List” document to discover the VM’s whose strength country has been modified. After reading that file it will determine that what number of vm’s have been there which failed all through election time and then will carry out restart of these VM’s.

Vmware Vsphere Interview Questions
Question 37. What Are The Things Which Ha Take Into Account Before Restarting Vm’s?

Answer :

HA has to take many stuff into issues before restarting VM’s in case of ESXi failure. These encompass:

CPU and reminiscence reservation inclusive of memory overhead.
Unreserved capability of host in cluster.
Restart priority of VM.
VM to host compatibility.
Number of dvi Ports required by VM and wide variety of dvPorts those are to be had.
Max no vCPUs to VM that may be run on a given host.
Restart latency.
Question 38. 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?

Answer :

If a virtual machine needs to be restarted by using HA and the virtual machine is within the method of being Storage vMotioned and the digital gadget fails, the restart manner isn't started till Vcenter informs the master that the Storage vMotion project has completed or has been rolled lower back.

Question 39. Will Master Election Happen If A New Esxi That Has Visibility To More Datastores Than Existing Master Is Introduced In A Cluster?

Answer :

No election will not occur even though the newly introduced ESXi has visibility to more datastores than grasp ESXi host. But if you reconfigure HA at the cluster then the newly added ESXi turns into master because it's far connected to greater wide variety of datastores.

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

Answer :

No removal of slave ESXi from cluster doesn’t has any impact on master. No election may be taking place in this example.

Vmware Horizon Interview Questions
Question forty one. Does Ha Seeks Assistance From Drs Before Starting Failover Of Failed Vm’s?

Answer :

Yes HA do takes help from DRS occasionally before beginning the failover of failed VM’s. If a cluster is configured with admission control policies and either “specify quantity of host screw ups cluster tolerates” or “percent” primarily based coverage is used then now and again it may take place that assets aren't completely available on single host and is scattered at some stage in the cluster. In that case HA will wait before acting failover of VM’s and ask help of HA to defragment the sources.