1.
Explain
the physical topology of Virtual Infrastructure 3 Data Centre?
A
typical VMware Infrastructure data center consists of basic physical building
blocks such as x86 computing servers, storage networks and arrays, IP networks,
a management server and desktop clients.
2.
How
do you configure Clusters, Hosts, and Resource Pools in VI3?
A
cluster is a group of servers working together closely as a single server, to
provide high availability, load balancing and high performance. A host is
a single x86 computing server with individual computing and memory resources.
Resource pools are allocation of the available resources in to pieces for the
proper distribution.
3.
What
are resource pools & what’s the advantage of implementing them?
A
VMware ESX Resource pool is a pool of CPU and memory resources. Inside the
pool, resources are allocated based on the CPU and memory shares that are
defined. This pool can have associated access control and permissions. Clear
management of resources to the virtual machines.
4.
Explain
why VMware ESX Server is preferred over Virtual Server or Workstation for
enterprise implementation?
For
better resource management as it has a virtualization layer involved in its
kernel, which communicates with the hardware directly.
5.
In
what different scenarios or methods can you manage a VI3 ?
Using
the Virtual Infrastructure Client we can manage one esx server, using virtual
center we can manage more than 1 esx server.. and also we can use service
console to manage it.
6.
Explain
the difference between access through Virtual Infrastructure Client (vi
client), Web access, Service Console access (ssh)?
Using
VI Client we can access the ESX server as well as Virtual Center Server also,
here we can use UNIX type of authentication or windows type authentication. But
to access the service console, we should use UNIX type of authentication
preferably even though we can access the service console through ad
authentication using esxcfg-auth, but it does not support all functions to work
on, all the functions are available only with root account which is based on
red hat Linux kernel. Using the web access also we can manage virtual center as
well as a single host. But all the enterprise features are not supported.
7.
Console
access to the Service Console
The
disadvantages to this mode are
You
must be at the console (or connect using an IP KVM) and
You
must know Linux to accomplish your task (no GUI).
8.
SSH
to the Service Console
You
can SSH to the console prompt of an ESX server and receive the same Linux text
console access as I showed above. Telnet is not allowed. To use this method,
the ESX server must be working on the network and you must have an SSH client
on your PC to connect. Again, in this mode, you don't get a GUI interface.
9.
VMware
Virtual Infrastructure (VI) Web Access to the ESX Server
This
is the VMware VI Web Access interface. The benefit to using this is that you
get a GUI client for your ESX server without having to install a client on your
local machine. The downside to the web interface is that you can only perform
basic ESX functions like controlling existing machines (start/stop/pause) and
console remote access. You cannot add new VMs, work with VM storage, or VM
networks. Still, this is a great interface if you just need to check the status
of your ESX VMs, restart a VM, or use console remote control.
10. VMware Virtual Infrastructure Client (VI Client) to the
Server
The
benefits to the VI client are that you have full access to do whatever is
needed on the ESX Server and you get a GUI client to do it in. The only
downside is that you must install the VI client application to do this.
However, the installation is negligible and the VI client is the absolute best
way to administer your ESX Server.
11.
VMware
Virtual Infrastructure Client (VI Client) to the Virtual Center Server (VC
Server)
From
this VI VC interface, you can manage all ESX servers, VM storage, VM networks,
and more. Virtual Center, of course, is an optional product that requires
additional licenses and hardware.
12.
Explain
advantages or features of VMware Virtual Machine File System (VMFS)?
It’s
a clustered file system, excellent support for sharing between ESX servers in a
cluster.
Features
ü Allows access by multiple ESX Servers at the same time by
implementing per-file locking. SCSI Reservations are only implemented when LUN
meta data is updated (e.g. file name change, file size change, etc.)
ü Add or delete an ESX Server from a VMware VMFS volume
without disrupting other ESX Server hosts.
ü LVM allows for adaptive block sizing and addressing for
growing files allows you to increase a VMFS volume on the fly (by spanning
multiple VMFS volumes)
ü With ESX/ESXi4 VMFS volumes also can be expanded using LUN
expansion
ü Optimize your virtual machine I/O with adjustable volume,
disk, file and block sizes.
ü Recover virtual machines faster and more reliably in the event
of server failure with Distributed journaling.
Limitations
ü Can be shared with up to 32 ESX Servers.
ü Can support LUNs with max size of 2TB and a max VMFS size of
64 TB as of version 4 (vSphere).
ü "There is a VMFS-3 limitation where each tree of linked
clones can only be run on 8 ESX servers. For instance, if there is a tree of
disks off the same base disk with 40 leaf nodes in the tree, all 40 leaf nodes
can be simultaneously run but they can only run on up to 8 ESX hosts."
ü VMFS-3 limits files to 262,144 (218) blocks,
which translates to 256 GB for 1 MB block sizes (the default) up to 2 TB for 8
MB block sizes.
13.
What
are the types of data stores supported in ESX3.5?
iSCSI data stores, FC SAN
data stores, Local VMFS, NAS and NFS
14. How can you configure these different types of datastores on
ESX3.5?
If
we have FC cards installed on the esx servers, by going to the storage option,
we can scan for the luns.
15.
What
is Vmware Consolidate Backup (VCB)? Explain your work exposure in this area?
VMware
Consolidated Backup is a backup framework, which enables 3rd party
tools to take backups. VCB is used to help you backup your VMware ESX virtual
servers. Essentially, VCB is a "backup proxy server". It is not
backup software. If you use VCB, you still need backup software. It is commonly
installed on its own dedicated Windows physical server. Here are the benefits
of VMware's VCB:
ü Centralize backups of VMware ESX Virtual Servers
ü Provide file-level backups of VMware ESX Virtual Servers -
both full and incremental (file level backup available to only Windows guests)
ü Provide image-level backups
ü Prevent you from having to load a backup agent on every
Virtual Machine
ü Prevent you from having to shutdown Virtual Machines to get
a backup
ü Provides LAN-Free backup because the VCB server is connected
to the SAN through your fibre channel adaptor
ü Provides centralized storage of Virtual Server backups on
the VCB server, that is then moved to your backup tapes through the 3rd party
backup agent you install
ü Reduces the load on the VMware ESX servers by not having to
load a 3rd party backup agent on either the VMware ESX service console or on
each virtual machine.
ü Utilizes VMware Snapshots
Basically, here is how VCB works:
ü If you are doing a file level backup, VCB does a snapshot of
the VM, mounts the snapshot, and allows you to backup that mounted
"drive" through VCB to your 3rd party backup software
ü If you are doing an image level backup of the VM, VCB does a
snapshot of the VM, copies the snapshot to the VCB server, unsnaps the VM, and
allows you to backup the copied snapshot image with your 3rd party backup
software.
16.
How
do you configure VMware Virtual Centre Management Server for HA & DRS? What
are the conditions to be satisfied for this setup?
HA
& DRS are the properties of a Cluster. A Cluster can be created only when
more than one host added, in that case we need to configure HA & DRS as
well to provide High Availability and Load balancing between hosts and for the
virtual machines.
17.
Explain
your work related to below terms :
ü VM Provisioning:
Virtual Machine Creation.
ü Alarms & Event Management: Alarms are used to know the status of the resource usage for
a VM. Events are used monitor the tasks that are taken place on the esx servers
or in the virtual center
ü Task Scheduler: Task
scheduler, if you want to schedule a task it will be used, for example if you
want move one VM from one host to another host or if you want shutdown/reboot a
VM etc.
ü Hardware Compatibility List: what are the hardware that compatible with ESX OS.
18.
What
SAN or NAS boxes have you configured VMware with? How did you do that?
Storage
team will provide the LUN information, with that we will add those LUNs to ESX
hosts from VM storage.
19.
What
kind of applications or setups you have on you Virtual Machines?
Exchange
server and Share Point, but these are for DEMO purposes, Citrix presentation
servers etc.
20.
Have
you ever faced ESX server crashing and Virtual Centre Server crash? How do you
know the cause of these crashes in these cases?
21.
Will
HA work if Virtual Center Server is down?
ü HA continues
to work if VC is down - the agents are
initially configured by virtual center, but HA operations are controlled by
local agents on ESX. VC does NOT monitor the ESX servers for HA. ESX servers
monitor each other.
DRS do not work while VC is down.
ü For DRS, the config and logic is completely in VC. For HA,
only the config is in VC. The logic is in the service consoles, and that's
where the reaction is coming from. VC will notice the HA reaction afterwards
when it connects to the service consoles the next time. No, Why because all
these futures are comes with Virtual Center only.
22.
What
are the situations which triggers vMotion automatically?
Resource
Contention between virtual machines (DRS)
Distributed
power management
23.
What
is DRS/HA/DPM/dvSwitch/FT/vApps/vSafe/vShields ? :-)
ü DRS : Distributed Resource Scheduling
ü HA : High Availability
ü DPM : Distributed Power Management
ü dvSwitch :
Distribute vSwitch – It’s a new
feature introduced in vSphere4.0
ü FT : Fault Tolerance for Virtual Machines – it’s a new feature
introduced in vSphere4.0
ü vApps : vApp is a container same as resource pool, but it is having
some features of virtual machines, a vApp can be powered on or powered off, and
it can be cloned too.
ü vmSafe : VMsafe's application programming interfaces are designed to
help third-party vendors create virtualization security products that better
secure VMware ESX, vShield Zones is a security tool targets the VMware
administrator.
ü vShield : VShield Zones is essentially a virtual firewall designed to
protect VMs and analyze virtual network traffic. This three-part series
describes vShield Zones, explains how to install it and provides useful
management tips. To begin, let's get started with the basics: what vShield
Zones is and how it works.
24.
What
are the requirements for FT?
25.
What
are the differences between ESX and ESXi?
ESX
is an OS with full features of virtualization; ESXi is a limited features OS
with 32MB image.
26.
Which
are the new features introduced in vSphere 4? *****
ü 64-bit hypervisor - Although
not everyone realized it, the hypervisor in ESX Server 3.5 was 32-bit. As a
result, ESX Server 3.5 couldn't take full advantage of today's more powerful
64-bit hardware platforms. ESX Server 4.0 uses a native 64-bit hypervisor that
provides significant performance and scalability enhancements over the previous
versions. However, the new hypervisor does require a 64-bit hardware platform.
ü Increased VM scalability - ESX Server 4.0's new 64-bit architecture provides
significant increases in scalability. ESX Server 4.0 supports virtual machines
(VMs) with up to 255GB of RAM per VM. In addition, the vSphere 4.0 Enterprise
Plus edition provides support for up to 8-way virtual SMP per VM. The other editions
support up to 4-way virtual SMP. These gains are available on both Windows and
Linux guests.
ü Hot add CPU, RAM, and virtual disks - This important enhancement in vSphere 4.0 is designed to
create a dynamic IT infrastructure through the ability to add CPU, RAM, and
virtual disks to a running VM. The hot add capability lets you dynamically
increase your VMs' performance during periods of high resource demands.
ü Thin provisioning - This
feature is nothing new to Microsoft virtualization users; vSphere now offers a
thin-provisioning feature that's essentially the equivalent of Hyper-V's
dynamic disks. Thin provisioning lets you create and provision a Virtual Hard
Disk (VHD), but the host uses only the amount of storage that's actually
required by the VM rather than using the VHD's allocated size.
ü VMware Fault Tolerance - Fault Tolerance is a new high-availability feature in
vSphere 4.0. Fault Tolerance works only between two systems. It uses a
technology called vLockstep to provide protection from system failure with
absolutely no downtime. VMware's vLockstep technology keeps the RAM and the
virtual processors of two VMs in sync at the instruction level.
ü vNetwork Distributed Switch—vSphere 4.0's vNetwork Distributed Switch lets you create
and share network configurations between multiple servers. The vNetwork
Distributed Switch spans multiple ESX Server hosts, letting you configure and
manage virtual networks at the cluster level. It also lets you move network
configuration and state with a VM when the VM is live migrated between ESX
Server hosts.
ü IPv6 support - Another
enhancement in vSphere 4.0 is support for IPv6. Many organizations are planning
to move to IPv6. vSphere's IPv6 support lets customers manage vCenter Server
and ESX Server hosts in mixed IPv4/IPv6 network environments.
ü vApps—vApps
essentially lets you manage as a single entity multiple servers that comprise
an n-tiered application. Using vApps, you can combine multiple VMs, their
interdependencies, and their resource allocations together as a unit. You can
manage all the components of the vApps as a single unit, letting you power off,
clone, and deploy all the vApps components in the same operations.
ü vSphere Host Update Utility—The new vSphere Host Update Utility lets you centrally
update your ESXi and ESX Server 3.0 and later hosts to ESX Server 4.0. The UI
displays the status of the remote updates in real time.
ü VMware vShield Zones—VMware's
new vShield Zones let customers enforce network access protection between VMs
running in the virtual data center. The vShield Zones feature lets you isolate,
bridge, and firewall traffic across vCenter deployments.
27.
Which
are the traffic shaping options available to configure?
28.
What
are promiscuous modes?
If
the promiscuous mode is enabled for a switch, the traffic sent that switch will
be visible to all vm’s connected to that switch. I mean, the data will be
broadcasted.
29.
What
makes iSCSI and FC different?
Addressing
Scheme, iSCSI relies on IP and FC not, and the type of transfer of data also.
In FC the data transferred as blocks, in iSCSI the data transferred as files.
The cabling also, FC uses Fiber cable and iSCSI uses RJ45.
30.
What
is the format for iSCSI addressing?
IP
Address
31.
VM's
Task Manager shows performance normal, but vCenter reports high resource utilization,
what is the reason?
Search
KEY WORDS : VM's performance normal, vCenter reports high resource
utilization
32.
What
are the different types of memory management tricks available under ESX?
33.
What
is vmmemctl?
34.
http://pubs.vmware.com/vi3/resmgmt/wwhelp/wwhimpl/common/html/wwhelp.htm?context=resmgmt&file=vc_advanced_mgmt.11.24.html
35.
How
we can list pNICs & status using command line?
ifconfig
–a
36.
What
is resource pool? What are the uses of it?
A
resource pool is a logical abstraction for flexible management of resources.
Resource pools can be grouped into hierarchies and used to hierarchically
partition available CPU and memory resources.
37.
Ask
about how HA works.
VMware
HA provides high availability for virtual machines by pooling them and the
hosts they reside on into a cluster. Hosts in the cluster are monitored and in
the event of a failure, the virtual machines on a failed host are restarted on
alternate hosts.
38.
Is
HA dependent on virtual center
(Only
for Install)
39.
What
is the Maximum Host Failure allowed in a cluster
(4)
40.
How
does HA know to restart a VM from a dropped Host
(Storage
lock will be removed from the metadata)
41.
How
many iSCSI targets will ESX support
8
for 3.01, (64 for 3.5)
42.
How
Many Fiber Channel targets
(256)
(128 on Install)
43.
What
is VMotion
(Ability
to move running vm from one host to another)
44.
What
is virtual SMP –
When
and why should you give a vm multiple vCPUs - part of their answer would be
that best practice is to start with a single vCPU because of you can run into performance
issues do to CPU scheduling
45.
Ask
what version of Linux kernel does ESX run
If
they are truly experienced they should say ESX is not Linux and does not use a
Linux kernel - and give them an extra poijnt if they explain that the service
console runs a modified version of Red Hat Ent 3 –
46.
Does
HA use vMotion?
The
answer is no - vm stops and restarts on ESX other host
47.
What
is the different when you use VIclient connect to VC and directly to ESX server
itself.
When
you connect to VC you manage ESX server via vpxa (Agent on esx server). Vpxa
then pass those request to hostd (management service on esx server). When you
connect to ESX server directly, you connect to hostd (bypass vpxa). You can
extend this to a troubleshoot case, where connect to esx see one thing and
connect to VC see another. So the problem is most likely out of sync between
hostd and vpxa, "service vmware-vpxa restart" should take care of it.
48.
What
was the most difficult VMWare related problem/issue you faced in a production
environment and what were the specific steps you took to resolve it?
49.
HA
issues – because of DNS problems, the hosts are unable to communicate together.
Corrected by adding all servers ip’s in each server’s /etc/hosts file
50.
VM
was not powered up – because the swap file was locked by another host, when I
try to power on the vm its not powering up. After releasing the lock its
powered on.
51.
When
was the last time you called VM Support and what was the issue?
Licensing
related issues.
52.
What
was the most performance intensive production app that you supported in VMware
and what were the some of the challenges that it posed?
In
exchange SharePoint demo project, getting lot of VLAN issues. (its my
experience, you can say yours)
53.
How
would you determine that a perf intensive app is a good candidate? Spefically
what tools would you use to identify candidates. Specifically inside those
tools what metrics would you use?
54.
What
is yor philosophy on how much of the data center can be virtualized? (If the
interviewer wants max virtualization, but the interviewee is not convinced that
this is a good idea, this could be a deal breaker)
55.
What
is your opinion on the virtualization vendors (MS vs VM vs Citrix vs etc) and
why? (Just trying to figure out if the candidate is keeping up with this ever
changing virtualization market)
56.
I
believe another good question would be to ask the candidate to briefly describe
VST, VGT & EST mode and 802.1Q trucking. I say this because networking is
such an important part of VMware implementations and ongoing support.., do you
really want a VMware engineer working in your environment if they lack the
knowledge of these concepts (+unless of course they are only delegated with low
level permissions for generic VM operations+)
More
information on this mode’s can be found here:
Also
ask the candidate to explain why one mode would be used as opposed to another?,
remember that there can be numerous reasons for the use of different modes
depending on your company/client's network, security policies etc..
57.
If
you are interviewing for a consultant role it would also be a good scenario to
provide a brief overview of a fictional network and ask the candidate to do a
whiteboard draft of how the network would be layed out if say the ESX servers
have 6 NIC's or 8 NIC's etc.. etc...
59.
What
are notable files that represent a VM?
.vmx – configuration settings for VM
.vmxf – configuration settings used to support an XML-based VM
configuration API
.vmtx – configuration settings for a Template VM (replaces the
.vmx file)
.vmdk – virtual disk file. (Note: if a thick disk is used, a
–flat.vmdk file that represents the actual monolithic disk file will exist but
will be hidden from the vSphere Client.)
.nvram – non-volatile memory (BIOS)
60.
.vswp – swap file used by ESX/ESXi per VM to overcommit
memory, i.e. use more memory than physically available. This is created by the
host automatically when powering on a VM and deleted (default behavior) when
powering off a VM. Swap files can remain and take up space if a host failed
prior to shutting down a VM properly. Normally the swap file is stored in the
location where the VM configuration files are kept; however the location can be
optionally located elsewhere—for example, locally for performance reasons and
if using NAS/NFS, local swap should be used.
61.
Host Profiles
What licensing is required for Host
Profiles? Available with vSphere Enterprise Plus edition.
62.
Can Host Profiles work with ESX/ESXi 3.x hosts?
No. Only starting with ESX/ESXi 4.0.
63.
Can Host Profiles be used with a cluster running both ESX
and ESXi hosts?
ü Yes, but remember to use an ESX host and not an ESXi host to
create a profile for use.
ü In theory, Host Profiles should work with mixed host
clusters, as it translates ESX to ESXi, but be careful as there are enough
differences between ESX and ESXi that can lead you to make self-inflicted
errors when applying Host Profiles. The easiest method is to create clusters
that are homogeneous and maintain two different profiles for these two types of
clusters.
64.
Can Host Profiles work when using the Cisco Nexus 1000v?
No, because Host Profiles was
designed with the generic vNetwork Distributed Switch. The Cisco Nexus 1000v
switch gives administrators finer-grained control of the networking beyond what
Host Profiles can apply.
65.
What are host profiles?
A set of best practiced
configuration rules, which are can be applied to entire cluster or to an
individual host. So that all the hosts in sync with each other, this will avoid
vmotion, drs and ha problems.
66.
Could not power on VM: no swap file
My ESXi 3.5 machine runs 8-10 VMs
(Win2k3 and WinXP) normally. At the moment, 5 of them are complaining that they
cannot Power On. They seem to start and then complain "Could not power on
VM: no swap file". I had a look with the data browser. It's a small
installation, so the vswp files ought to be in the same directory as the vmx
file (I did not inttionally put them anywhere else). Of course I don't see a
vswp file there because the machine is not running. I don't know enough about
the vmx file structure to identify if anything is wrong in the specifications.
I have downloaded one of the vmx files and attached it here. Please either tell
me what to change in that vmx file, or suggest another approach to get the
machines to start.
67.
What are the available Storage options for virtual machines
? Raw device mappings, VMFS
68.
What are the differences between Virtual and Physical
compatibility modes when mapping the Raw Devices to virtual machines?
ü You can configure RDM in two ways: Virtual compatibility
mode—this mode fully virtualizes the mapped device, which appears to the guest
operating system as a virtual disk file on a VMFS volume. Virtual mode provides
such benefits of VMFS as advanced file locking for data protection and use of
snapshots.
ü Physical compatibility mode—this mode provides access to
most hardware characteristics of the mapped device. VMkernel passes all SCSI
commands to the device, with one exception, thereby exposing all the physical
characteristics of the underlying hardware. In this mode, the mapping is done
as follows, when we create a mapping, the configuration stored in a file and
that file is stored with the vm files in data store. This file points to the
raw device and makes it accessible to the vm.
69.
What are RDM Limitations?
ü RDM limitations There are two types of RDMs: virtual
compatibility mode RDMs and physical compatibility mode RDMs. Physical mode
RDMs, in particular, have some fairly significant limitations:
v No VMware snapshots
v No VCB support, because VCB requires VMware snapshots
v No cloning VMs that use physical mode RDMs
v No converting VMs that use physical mode RDMs into templates
v No migrating VMs with physical mode RDMs if the migration
involves copying the disk
v No VMotion with physical mode RDMs
ü Virtual mode RDMs address some of these issues, allowing raw
LUNs to be treated very much like virtual disks and enabling functionality like
VMotion, snapshotting, and cloning. Virtual mode RDMs are acceptable in most
cases where RDMs are required. For example, virtual mode RDMs can be used in
virtual-to-virtual cluster across physical hosts. Note that physical-to-virtual
clusters across boxes, though, require physical mode RDMs.
ü While virtual disks will work for the large majority of
applications and workloads in a VI environment, the use of RDMs--either virtual
mode RDMs or physical mode RDMs--can help eliminate potential compatibility
issues or allow applications to run virtualized without any loss of functionality.
ü I previously posted some questions related to VMware
already. And the post has very good response. You can read it here -
http://www2.isupportyou.net/2010/06/vmware-interview-questions-tips.html
.vmss – suspend file (if placed into suspend power mode)
.vmsd – for snapshot management
.vmsn – snapshot file