- VMware Interview Questions
Explain what is hypervisor
A hypervisor is a program that enables multiple operating systems to share a single hardware host.
The hypervisor controls the resources and host processor, allocating
what is required for each operating system
in turn and make sure that the guest operating system cannot disrupt each other.
Explain
VMware DRS?
VMware DRS stands for Distributed Resource Scheduler; it dynamically balances resources across various host under a cluster or resource pool.
Define the term
’VMKenel’.
VMWare Kernel is a proprietary kernel of
VMware. It needs an operating system to boot and manage the kernel. A service console is being offered whenever
VMWare kernel
is booted.
What is the use of Promiscuous Mode?
Promiscuous mode is useful when you want to run a virtual machine with network sniffers helps you to capture packet of that network.
Moreover, if the promiscuous mode set to accept, all the communication is visible to all the virtual machines.
What is Cold and Hot Migration?
When you migrate powered off or suspended,
it is known as cold migration. When you migrate your running power on virtual machines,
it is known as hot migration.
What is Virtual Desktop Infrastructure?
Virtual Desktop Infrastructure which also known as VDI allows you to host the desktop operating system on the centralized window server in a data center.
It is also known as server-based computing as it is the variation on the client-server computing model.
Explain the importance of snapshot in
VMWare
A
VMWare snapshot is a copy of a virtual machine disk file which is used to restore a VM to a specific point
in time when the system fails, or system error occurs.
What is
VVol?
Virtual Volume known as
VVol is a new VM
disk management feature concept introduced in
vSphere 6.0. It enables array-based operation at the virtual disk level.
It is automatically created when a virtual disk
is created in a virtual environment.
Can we do
vMotion between two data centers?
Yes, we can do
vMotion between two
datacenters. However, for this VM should
be powered off.
What is RDM?
RDM is a sort form of Raw Device Mapping. It is a file stored in VMFS volume which acts as a proxy for a raw physical device. It allows you to store virtual machine data directly on LUN.
What is NFS?
NFS is a Network file system. It is a file sharing protocol which ESXI host used to communicate with the NAS device. It is a specialized store device which connects to a network and can provide file aces service to ESXI hosts.
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- Explain what happens to a Virtual Machine after the host which it is running on, fails.
First,
you should explain that the VM
is forcefully powered off.
Next, ask if the host was in a correctly configured HA cluster (If it isn’t then nothing else happens to the VM)
If the Host is HA enabled, then ask what the Virtual Machine restart policy is. If it’s
disabled then
the VM will not be restarted on other hosts.
Ignoring the HA master election process, the simple answer is that the Virtual Machine will
be rebooted on another
ESXi host in the cluster.
Mention that there are things that will stop a Virtual Machine from being restarted on other hosts such as Admission Control settings & resource availability on the host.
The key thing to remember is that HA does NOT trigger a
vMotion.
When should Promiscuous Mode
be enabled on a Virtual Switch
Promiscuous Mode is a
vSwitch and
Portgroup setting that allows for Virtual Machines to receive all traffic within the same
vSwitch or
Portgoup (depending on where you set the configuration)
Typical use cases for this are packet sniffing applications.
Name 3 benefits of installing
VMware Tools on Virtual Machines
Enables features such as Guest Introspection for NSX / agentless antivirus
Installs the VMXNET3 driver for improved network performance.
Allows the ability to copy and paste between the VM and desktop (some other settings might need to
be enabled first)
What techniques are available to
ESXi to reclaim memory?
Transparent Page Sharing (TPS)
– Note that as of
vSphere 6.0, this
is disabled by default.
Ballooning
– Requests
VMware tools to “inflate a memory balloon” inside the VM until
excess memory is released back to
ESXi.
Memory Compression.
Swapping
– This is the last option that
ESXi will use to reclaim memory because it is the most disruptive to performance as memory gets swapped out from real memory onto disk
What is the impact of using Thick Eager Zeroed disk provisioning for VMDKs?
This disk type will zero out all data on the disk before allocating the VMDK to the Virtual Machine.
This has some performance benefit to the VM because it doesn’t have to zero a block before it can
be written to.
The negative side is that it takes longer to provision the VMDK to the VM (since it has to zero all blocks first) and it has a measurable, sustained IO hit on the storage system
What are the main benefits of a Distributed Switch?
Central Management of all
ESXi host’s networking, meaning that there is only one switch to manage rather than one per host.
The ability to enable Network IO Control (NIOC)
NetFlow support.
Name 3 Virtual Machine Files
VMX
– The Virtual Machine configuration file
NVRAM
– The VM’s BIOS file
VMEM
– The VM’s
pagefile
VMSD
– VM Snapshot state file
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