25 VMware Interview Questions: Tough & Technical
25 VMware Interview
Questions: Tough & Technical
Hello and welcome to Growth
is life. In this post I’ll share a list of 25 VMware
interview questions that I have crafted to screen for the best talent to manage
and support VMware vSphere.
Why is my list any different from the hundreds
of others on the web?
Well, first of all, it’s not a VCP test
brain-dump…
Secondly, these interview questions are
carefully crafted to narrow the talent pool to the most qualified, not the most
memorized.
These interview questions require hands on experience to answer!
VMware Technical Interview Questions
The list of questions below is intentionally
broken up into 5 groups:
1.
System Requirements for
ESXi 5.5/6,x
2.
ESXi 5.5/6.x
Installation
3.
System Requirements for
vCenter
4.
vCenter Installation
5.
Managing vSphere
Resources
These 5 groups will test for technical
proficiency that an experienced VMware adminis07ator will [or should have].
The list is also what I use when interviewing
someone at an adminis07ator level who will manage the day-to-day support,
build, and provisioning of:
·
vCenter
·
ESXi hosts
·
virtual servers
·
virtual networks
·
virtual storage
Note: This list of questions may also be used
for screening vSphere Engineers or Architects.
System Requirements for ESXi
1.
Your company has a bunch
of unused server hardware and you have been asked to build a vSphere
environment. But before you start you want to make sure it is supported by the
ESXi version you plan to install. Where would you find a list of hardware that
is supported?
Answer: You would check the VMware Compatibility
Guide http://www.vmware.com/resources/compatibility/
2.
Your hardware is on the
compatibility list and now you need to know what the minimum CPU and memory
requirement of an ESXi host when building a 64bit OS that will take full
advantage of ESXi features ?
Answer: 2 CPU Cores and 8 GB memory (bare
minimum)
3.
Before you start
installing software what must be enabled in the server BIOS in order to run
ESXi?
Answer: The NX/XD bit needs to be enabled.
4.
You also have an old
pile of network adapters to choose from. Where would you find a list of network
adapters (NIC) that are supported by the version of ESXi you are installing?
Answer: You would check the VMware Compatibility
Guide (same link as above)
5.
One of the servers you
found wasn’t on the list and now you have a problem that is causing ESXi to
purple screen so you call VMware for support. What would happen if they found
out your hardware was not supported?
Answer: When hardware is not supported there are
known issues that will happen and VMware cannot help to resolve problems due to
unsupported hardware.
Unpacking the ESXi hardware interview questions.
Why are these questions about server hardware
important?
Since 2006 I have had the awful job of having to
clean up behind admins that would build vCenter and ESX/ESXi on any hardware
they found. I’m guilty of it myself!
This is not only a bad practice but it also
leads to unplanned maintenance and costly outages that impact users and
customers.
ESXi will run on just about any hardware but that doesn’t mean it
should.
An experienced vSphere admin will know better
than to waste time (and a costly license) 07ying to run a 64bit OS on a server
that doesn’t support it.
6.
You’ve done this a
hundred times. What are 3 methods that can be used when doing an Interactive
ESXi installation?
Answer: Boot from a CD/DVD, boot from a USB, and
PXE boot from a deployment server on the network.
7.
After so many ESXi
builds you have figured out a faster way to do the install using a script.
What’s the main difference between an interactive ESXi installation and a
scripted installation?
Answer: The interactive install will require you
to follow along and fill in the configuration information whereas, in a
scripted install, the configuration information will be queried from an
unattended text file (boot.cfg). Note: ESXi uses a Kickstart installer similar
to Linux.
8.
You can install ESXi in
your sleep. What is the command to access the installer window on ESXi 5.5?
Answer: Shift+O will get you to the runweasel
command prompt.
9.
Darn, one of your
servers is not loading. What’s the first thing to double-check when having a
problem installing ESXi?
Answer: Make sure the hardware clock is set to
UTC and the NX/XD bit is enabled in the BIOS.
10.
You’ve typed this stuff
in a million times. Name 5 of the 10 bits of information required when
installing ESXi?
Answer: Keyboard Layout, VLAN ID, IP Address,
Subnet Mask, Gateway, Pri DNS, Sec DNS, Host Name, Installation Location, Root Password.
Now let’s unpack VMware interview questions
about ESXi Installations.
ESXi is actually easy to install and setup;
however, problems do arise when there are different admins or teams building
out environments that share the same network, storage, and server resources. It
is very important to have a standard build process so all hosts are built the
same way every time.
Finding a good vSphere admin who can follow your
standard, someone who can answer these basic questions, is a good start.
System Requirements for vCenter
11.
You decided not to run
the vCenter appliance. What’s the minimum hardware requirements for a vCenter
5.x server?
Answer: It depends on whether other vSphere
services such as single sign-on, inventory service, and the database will be
running on the same hardware with vCenter.
12.
You’re going to upgrade
vCenter and the old vCenter is running on Windows Server 2003. What Windows
Operating System is required for vCenter 5.x/6.x?
Answer: Windows 2008 SP2
13.
You’re creating a list
of ports you need the network admin to open on the firewall. What is port 902
used for on vCenter?
Answer: Port 902 is the default port vCenter
uses to send data to hosts managed by vCenter.
14.
The old vCenter was
running MS SQL Express but you are building 10 ESXi hosts. What’s the
difference between using MS SQL Server Express and MS SQL Server for vCenter?
Answer: MS SQL Server Express is for vSphere
installations with up to 5 ESXi hosts and 50 virtual servers.
15.
Your new boss doesn’t
like MS SQL and asked you to use Oracle. Does vCenter support Oracle 11c or
12c?
Answer: Yes, but the JDBC driver must be
installed manually.
Let’s review vCenter Interview Questions.
vCenter is at the heart of vSphere and when it’s
not properly setup there will be problems!
These problems may be as small as a frus07ated
admins who can’t access and support virtual servers from a cen07al management
console. Or as large as a full-blown outage and corruption of the vCenter
database.
For example, if a vSphere clouds grows too fast the additional
load on hardware and system resources can cause performance problems that in
worst cases can require a complete rebuild of vCenter on bigger hardware.
Fortunately, each ESXi host can be managed separately if cen07al management via
vCenter is lost.
An experience vSphere admin who can answer these
questions will likely know this work-around.
Managing vCenter Resources
Before we dive into the final 10 questions I
want to s07ess how important finding a team player that will work closely with
storage and network admins really is.
Tip! Pay close attention for any sign that the person you are
interviewing does not think he/she owns your vSphere Cloud!
Storage is everything!
16.
You’ve learned over the
years there’s more to vSphere than server hardware. What other 2 resources are
just as important as servers and need to be properly planned out when designing
and building a vSphere Cloud?
Answer: Storage and network resources are
crucial for all vSphere Clouds.
17.
VMware vSphere give you
options. What are the 4 typical ways storage can be added to a vSphere?
Answer: Storage can be added via iSCSI, FC, NFS
and local disk (including DAS).
18.
When setting up a new
datastore how many VMFS file systems should be created per LUN?
Answer: The best practice is to only create 1
VMFS file system per LUN.
19.
What is the best plan
for a storage failure that impacts multiple datastores?
Answer: Always have a backup of the VMs on a
separate storage environment that can be used to restore the lost virtual
servers.
20.
Your host is a beast,
dual socket with 8 core CPUs and 192 GB of memory. How many virtual servers can
be added to a 1TB datastore?
Answer: It depends on the size of the VMs and
the performance of the storage. Higher performing storage can be filled to
capacity but space should be left for data growth and snapshots. A datastore
should never be allowed to fill up 100%.
Unpacking these VMware Storage Qs.
Managing storage in a vSphere is an important
job that can get a junior vSphere admins in big 07ouble!
Regardless of the protocol (iSCSI, NFS, FC) it
requires a certain skill set which only comes with time and experience. Every
new ESXi hosts which is added to vSphere requires someone to know how to
balance the workloads across various storage tiers: local disk, SATA, SAS and
SSD (depending on the needs of the environments and applications).
Far too many new VMware admins have learned the hard way that “Not all storage is the same” and very quickly a junior admin can cause an outage on a business
critical database server simply by vMotioning a VM to a datastore that looks
empty.
Networking is everything, too!
21.
This is a tough VMware
interview question created just for you. Name 4 things that happen on the
VMkernel networking layer?
Answer: vMotion, IP storage (iSCSI/NFS), Fault
Tolerance and Virtual SAN.
22.
You have a VCP so this
should be an easy interview question. What are 2 ways a vSphere admin can
separate 07affic from distinct environments (ex. Production and test) on the
same hosts.
Answer: Either by creating separate vSwitches
using dedicated NICs or if NICs are not available by creating separate port
groups using different VLAN IDs on the same vSwitch.
23.
True or false. A
Dis07ibuted Virtual Switch is very much like a physical switch that detects
which VMs are logically connects to each port and uses that information to
forward network 07affic. Hint: It is not used for monitoring and adminis07ation
across a datacenter.
Answer: False. A Dis07ibuted Virtual Switch acts
as a single switch across all hosts in a datacenter to provide cen07alized
provisioning, adminis07ation, and monitoring of virtual networks.
24.
Another True or false.
NIC teams are “normally” put in active/active mode to allow fail-over in the
event of a hardware failure.
Answer: False again. NIC teams are normally put
in active/standby mode to allow fail-over in the event of a hardware failure.
You can use active/active but this would not be standard and would require port
channeling at the physical switch.
25.
This is a 07ick question
so think about it! How many physical NICs are needed in an ESXi hosts for
hosting 25 virtual servers on iSCSI storage split between 2 diverse
environments (web/app).
Answer: The answer is purely subjective. It
depends on how much separation is needed for performance and the level of
redundancy built into the design for hardware failure. At minimum, maybe 2 (1
for data and 1 for VMkernel) but more should be used.
And finally, let’s review the Network Questions.
Since 2007, I estimate 80% of all the VMware
problems I have dealt with were network or storage related. That’s not to say
it was the network or storage admins fault. No, in most cases it was the VMware
admins fault for not communicating and properly calculating the requirements
before he/she asked for IP addresses or storage LUNs.
Like I said in the beginning. These questions
are not for practicing to take a VCP test. They are designed to gauge the level
of experience someone who is applying for your VMware admin or engineer job has
before you give them the keys to start managing your company’s jewels.
More IT Interview Questions:
What’s next?
I hope these VMware interview questions have
been helpful!
You don’t need to use them all … maybe asking
one question from each group during the screening call to start and then have
your technical team unload the rest during the face to face interview?
Also, if you noticed, I didn’t add any questions
about managing VMs. It’s because someone who can answer most or all 25 VMware
questions will surely have experience deploying and supporting virtual servers.
That’s not all. I’m sure your technical team
will have a few whoppers of their own!
Need an experienced Pro to screen your VMware
applicants? Contact me on LinkedIn!
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