Interview Questions.

Question 1. What Is The Default Invocation Period For Drs. Can We Change This. If Yes Then How?

Answer :

The default invocation length is three hundred seconds (5 mins). But this could be modified through the configuration report vpxd.Cfg.

We have to exchange the fee of <pollperiodsec> as proven underneath:

<config>

<drm>

<pollperiodsec>

three hundred

</pollperiodsec>

</drm>

</config>

Just exchange the cost 300 to a custom fee described via you. The variety of supported value is 60 secs to 3600 secs.

Question 2. What Is The Role Of Vpxa In Drs?

Answer :

VPXA is the vCenter agent that runs interior Esxi hosts and it allows a 2 way communication between Esxi hosts and vCenter Server.

VPXA is liable for:

Keeping the reputation of Esxi and VM’s in sync
It sends information to vCenter server when a VM’s energy kingdom is modified or a VM is vMotioned from one host to different.
DRS makes use of this data that's provided with the aid of Esxi hosts to vCenter server for calculating the load stability and proposed migrations in case of cluster imbalance.
Domain Name System(DNS) Interview Questions
Question three. Will Drs Work If Vcenter Server Is Down? If No Then Explain Why Drs Is Dependent On Vcenter Server?

Answer :

No DRS will no longer paintings if vCenter Server is down.

DRS relies upon upon vCenter server for information like present day electricity state of virtual machines, trade in electricity state of any VM, number of datastores to which Esxi hosts are linked and the reminiscence and cpu configurations of a VM.

DRS will use these kinds of facts even as calculating the weight at the cluster and presenting migration guidelines whilst a cluster needs to be balanced.

Question four. How Drs Calculates There Are Imbalances In Cluster? What Are The Things That Drs Takes Into Account For Determining This?

Answer :

 To calculate the cluster imbalance, DRS compares the Current Hosts Load Standard Deviation (CHLSD) to Target Hosts Load Standard Deviation (THLSD) and if

CHLSD < THLSD

Cluster is considered as imbalanced.

CHLSD Calculation:

DRS computes Normalized Entitlement (NE) of each Esxi hosts and the usual deviation related to it. NE is not anything however calculation of ways a lot resources are presently applied out of general sources. NE is calculated by means of summing up dynamic entitlements (utilization) of all VM’s which are going for walks on an Esxi host and diving this by way of Esxi host capacity.

So, NE= Dynamic Usage of all VM’s / Total host ability

THLSD Calculation:

THLSD is derived from DRS migration threshold that's defined on the time of configuring DRS. Each threshold level units extraordinary imbalance tolerance margin. The aggressive threshold sets a decent margin taking into account little imbalance, whilst conservative thresholds tolerates bigger imbalances.

Question five. What Is Drs Cost-benefit-risk Approach?

Answer :

DRS uses a price advantage risk technique to load balance a cluster. Before offering the migration tips for a VM to load stability a cluster,

DRS calculates three things:

Cost: What will be the price of migrating a VM from supply to destination host? Cost right here refers back to the CPU and reminiscence.

When a vMotion method in invoked on a VM, it reserves 30% of the cpu center (For 1 GB NIC) of that VM and one hundred% cpu center (For 10 GB NIC). This reservation is created on both source and vacation spot host. This reserves resources can’t be allotted to every other VM whilst vMotion is in progress. This can placed some pressure on an Esxi host when it is closely loaded.

Benefits: What could be the resource benefit that an Esxi host will get after migrating a digital machine to different Esxi ho st. If after the migration CHLSD value of the Esxi host comes down then DRS will take into account that migration as benefit.

Risk: Risk debts for possibility of abnormal loads. Suppose a VM has inconsistent and spiky needs of assets, then migrating such VM’s is not a great circulate because can be at the time of migration VM resource demand became low however after final touch of migration, VM’s aid needs  accelerated. In this case it is able to motive the growth in destination Esxi hosts CHLSD and again DRS has to perform migration of that VM to bring down CHLSD of the Esxi host in which that VM was migrated.

DRS recommends migrations if Benefit acquired due to a migration < fee related to that migration.

DHCP Interview Questions
Question 6. What Are The Factors That Affect Drs Recommendations?

Answer :

Following are the elements which affect the DRS suggestions:

1- VM length and Initial Placement: When a brand new VM is created or a VM is powered on, DRS selects a number in which this VM need to be initially placed. DRS prefers the registered host so long as placement of that VM in this host will now not motive cluster imbalance.

During placement of such VM’s DRS uses a worst case state of affairs as it doesn’t have ancient statistics for that VM. DRS assumes each CPU and reminiscence call for of this VM is same to its configured length.

Oversized VM’s can temporarily cause cluster imbalance and might motive needless migrations of lively VM’s.

2- PollPeriodSec (Length of DRS Invocation): The default fee of PollPeriodSec is 300 seconds. Range of PollPeriodSec is 60 sec to 3600 sec. Shortening this era will cause boom in vCenter overhead as cluster imbalance can be calculated often.

Increasing this cost decreases the frequency of cluster balance calculation and might go away your cluster imbalanced for longer period of times however lets in for large variety of vMotions due to lengthy invocation c programming language.

3- Simultaneous vMotion: vSphere five.1 allows eight concurrent vMotions on a single host with 10GbE abilties. For 1GbE, four concurrent vMotion can takes area. Also multi-NIC vMotion is supported in vSphere 5.1 so more than one active NICs and their combined bandwidth may be used for migration of a VM. In such surroundings VM’s might be migrated quick and cluster can be balanced in much less time.

Four- Estimated Total Migration Time: The migration time relies upon on variables like source and destination host load, active memory utilization of VM, link speed and available bandwidth+ latency of the physical community used by vMotion Portgroup.

Question 7. What Are The Use Cases For Vm-vm Affinity Rules And Vm-vm Anti Affinity Rules?

Answer :

VM-VM affinity: This is beneficial whilst you require that 2 of your VM’s ought to usually run collectively on an Esxi host. For E.G. Keeping front-cease and lower back-quit server of an application on equal ESXi host to lessen community latency between the two VM’s.

Another use case can be going for walks together identical forms of VM’s that are having identical sort of packages for you to get max blessings of obvious page sharing (TPS)

VM-VM anti-affinity: This is useful when you don’t want that 2 of your VM must run collectively. Keeping servers presenting same form of offerings on different host will offer resiliency

For Example: You will no longer want your DC and ADC run collectively on identical Esxi host because if that Esxi host goes down it is able to seriously effect your environment as both DC and ADC server has gone down collectively.

Another use case will be strolling net-server farms or clustered DB-servers in a virtualized environment.

Also, keeping away 2 VM’s from every different that are very aid in depth to stop them from monopolizing useful resource utilization.

VMware Infrastructure with ESX Server and VirtualCenter Interview Questions
Question eight. What Are The Use Cases Of Vm-host Affinity Rules And Vm-host Anti-affinity Rules?

Answer :

VM-Host affinity: This is beneficial when you want that your VM must run on a specific Esxi host handiest.

For Example: going for walks and oracle DB server which has socket based totally license. If your environment is having heterogeneous hosts than migrating such VM to a bunch which has one-of-a-kind CPU configuration can violates your license and can purpose problem.

VM-Host anti affinity: This is useful whilst you need that a particular VM should not run on a few precise Esxi hosts.

For Example: your surroundings has heterogeneous hosts and all of the hosts don’t have Numa structure and you want to get blessings of the vNuma inner your VM. In this example you will need your VM to run most effective on the ones servers which helps Numa.

Question 9. Can Drs Override “preferential Or Should Rules”. If Yes Then How And If No Then Why?

Answer :

Yes DRS can override have to policies. When regulations are configured inside DRS then DRS creates a rule listing and offer migrations recommendations in accordance with the rules described in rule list. But if the cluster imbalance cannot be solved even after strolling those migrations then DRS drops the rule of thumb list and re-run the load stability set of rules and  those migrations additionally which could spoil the have to regulations, in an effort to load balance a cluster in a better manner.

VMware ESXi Interview Questions
Question 10. Can Ha, Drs And Dpm Override “need to Or Mandatory Rules”?

Answer :

No HA, DRS and DPM can’t override have to regulations.

Question eleven. What Impact Does Must Rule Places On Drs, Ha And Dpm Operations?

Answer :

If a migration will purpose violation of need to rule then that migration can be cancelled by way of DRS.

IF DPM is trying to place a number in sleep mode for electricity saving however migration of VM’s jogging in this host can motive a must rule violation, it's going to save you DPM to position that host in sleep mode.

If HA is trying to restart VM’s after a bunch failure however if restart of some VM’s on a particular host can motive have to rule violation then HA will either restart those VM’s on a few exclusive host or could not restart them in any respect if no appropriate host is to be had for failover.

Windows Vmware Interview Questions
Question 12. If We Have Configured Some Rules (affinity Or Anti-affinity) In Drs The Will Those Rules Work If We Disable Drs On A Cluster?

Answer :

Yes guidelines might be in have an effect on even if we disable DRS without deleting the policies first.

Domain Name System(DNS) Interview Questions
Question 13. If On A Vm, Vm-host Affinity Should Rule Is Configured Then Can We Migrate That Vm On An Esxi Host That Is Not Part Of The Drs Cluster?

Answer :

No a VM can’t be migrated to an Esxi host that isn't a part of the DRS cluster

Question 14. What Are The Best Practices For Disabling Drs?

Answer :

Before disabling DRS it's far encouraged to delete all affinity and anti-affinity regulations and then proceed. Because if policies are not deleted and DRS is disabled, policies might be still in have an effect on and might affect cluster operations.

Question 15. What Are The Limitation That Are Put By Drs Mandatory Or Must Rules On A Cluster?

Answer :

If a mandatory rule is configured on a cluster then it could positioned following boundaries:

Limit DRS to choose hosts for load balancing
Limit HA to pick out host for failover
Limit DPM to pick out host to energy off
It can affect ability of DRS to defragment the cluster sources. At the time of failover HA can seeks assistance for DRS and might ask to defragment assets if a unmarried host isn't able to offer ok assets for failover.

VMware NSX Interview Questions
Question sixteen. If A New Drs Rule Is Created But That Rule Is Conflicting With Any Existing Rule Then Which Rule Drs Will Respect, Old Rule Or New Rule While Performing Drs Actions?

Answer :

If a new rule is conflicting with an old rule then new rule may be disabled automatically. DRS will opt for respecting the vintage rule.

Question 17. How Many Automation Levels Are There For A Vm In Respect To Drs? Can Vm Automation Level Override Cluster Automation Level?

Answer :

VM automation degree can override cluster automation level. From a VM prospective there are 5 automation tiers.

These are:

Fully Automated: Load balance and Initial placement can be performed by DRS robotically
Partially Automated: Load stability of the VM will be completed manually but preliminary placement may be achieved robotically
Manual: VM migration as part of Load balancing and preliminary placement will be both manual. DRS will simplest generate recommendation for that VM and administrator has to manually approve this advice.
Default: VM will inherit the DRS automation degree as described on the cluster level.
Disabled: DRS will no longer carry out any actions on that VM.
VMware Interview Questions