VMware vSphere Interview Questions

1.What are the products included in VMware vSphere 5.5 Bundle ?

• VMware ESXi
• VMware vCenter Server
• VMware vSphere Client and Web Client
• vSphere Update Manager
• VMware vCenter Orchestrator

2.What type of Hyper-visor VMware ESXi is ?

• VMware ESXi is Bare-metal hypervisor. You can directly install on server hardware.

VMware Hypervisor

3.What is the role of VMware vCenter server?

• vCenter provides a centralized management platform and framework for all ESXi hosts and their respective VMs. vCenter  server allows IT administrators to deploy, manage, monitor, automate, and secure a virtual infrastructure in a centralized fashion. To help provide scalability , vCenter Server leverages a back-end database (Microsoft SQL Server and Oracle are both supported, among others) that stores all the data about the hosts and VMs.

vCenter Server – Overview

4. Is it possible install vCenter server on Linux hosts ?

• No.But Pre-build vCenter appliance is available in VMware portal which is Linux based.You can import the appliance as virtual machine.

5.How to update the VMware ESXi hosts with latest patches ?

• We can update the ESXi hosts using VMware Update Manager(VUM). We can use this VUM add-on package on Windwos based vCenter server and Linux based vCenter server (vCenter appliance)

6.What is the use of VMware vSphere Client and vSphere Web Client ?

• vCenter Server provides a centralized management framework to VMware ESXi hosts.To access vCenter server, you need vSphere client or vSphere Web client service enabled.

vSphere Client

7.What is the difference between vSphere Client and vSphere web client ?

• vSphere Client is traditional utility which provides user interface to vCenter server. But from VMware vSphere 5 onwards,vSphere web client   is a primary interface to manage vCenter server.For vSphere client, you need install small utility .But vSphere Web client doen’t require any software. You can directly connect using web browser.But still VUM is managed through vSphere Client .

vSphere Client:

vSphere Client – Login

vSphere web-client:

vSphere web client

8.What is the use of VMware vCenter Orchestrator ?

• vCneter Orchestrator is used for automation on various vSphere products.

9.What are the features included in VMware vSphere 5.5 ?

• vSphere High Availabitliy (HA)
• vSphere Fault Tolerance
• vSphere vMotion
• vSphere Storage vMotion
• vSphere Distributed Resource Scheduler (DRS)
• virtual SAN (VSAN)
• Flash Read Cache
• Storage I/O Control
• Network I/O Control
• vSphere Replication

10.What is the use of vSphere High Availability(HA)? Where it can be applied ?

• VMware vSphere HA minimize the VM’s unplanned downtime by restarting the VM guests on next available server ESXi node inacase of failure on current ESXI node. VMware HA must be enabled to reduce the VM unplanned downtime.

VMware HA

VMware Storage I/O Control - VMware SIOC

SIOC is considered to be one of the finest addition to the VMware feature stack. In this blog we will discuss about SIOC and its impact on Disk usage.

Before discussing about SIOC, we should understand the relevance of VM based 'Disk Shares' in VMware. The disk share concept is simple and much alike Memory and CPU shares. When there is a resource constraint, the host will throttle the disk usage of  VMs by adjusting its Disk Queue Depth based on its share values. If all the VMs have the same Disk Share, the control over disk will be shared among all VMs. If the share value of a VM is high, it gets precedence over other VMs.


Simple and effective right...then why should VMware introduce a new feature called Storage I/O Control - SIOC.

The answer is simple, 'Disk Share' calculates the share value of VMs in a particular host whereas the relevance of SIOC comes in a cluster.

SIOC is configured for a particular datastore and will be disabled by default. Once enabled, SIOC gets active based on the value of the datastore latency. The current latency of datastore will be stored in the file called iormstat.sf which is hidden in the datastore. The default threshold value of latency is set to 30ms which is of course configurable. The threshold value can be changed based on the underlying storage technology. For eg: <20 and="" for="" ms="" nbsp="" sata.="" span="" ssd="">SIOC requires VMware Enterprise Plus license.

A datastore-wide disk scheduler (PARDA control algorithm) runs on each host sharing that datastore. This scheduler will be triggering 'Latency computation' and 'Window Size Computation' algorithms. 'Latency Computation' is used to detect if SIOC needs to throttle queues to ensure each VM gets its fair share. 'Window Size Computation' is used to calculate what this queue depth should be for your host. Once the queue depth is calculated by PARDA, the 'Local Host Scheduler' will take on from there. By default the queue depth is 32 and will be adjusted to a value calculated by PARDA which will be always higher than 4.

VMware recommends that this feature should be enabled for better VM performance. It is not at all advisable to leave a datastore unconfigured with SIOC, when other datastores in the same physical array is configured with SIOC.

Pictorial representation of SIOC scenario

Suppose we have 3 VMs with equal disk shares of 1000 each. 2 VMs are in one ESXi and the 3rd VM in another ESXi. When SIOC is disabled, even though all VMs are configured with equal shares,  the VM in the 2nd ESXi will enjoy more disk shares during resource constraint.

SIOC disabled

With SIOC enabled, VMs across hosts enjoys a fair share. 

SIOC enabled

VMware converter error: Unable to create a VSS snapshot of the source volume

Issue

VMware P2V conversion of Windows 2003 server fails with the below error :

FAILED : Unable to create a VSS snapshot of the source volume(s). Error code:
2147754774 (0x80042316)

Cause

This is a known issue with Microsoft and occurs when there is an issue with Windows Volume Shadow Copy  Service (VSS).

Resolution


Re-register Windows Volume Shadow Copy  Service (VSS) to resolve this issue.

Steps to re-register VSS (From Microsoft article):

1. Click Start, click Run, type cmd, and then click OK.

2. Type the following commands at a command prompt. Press ENTER after you type each command.

cd /d %windir%\system32
Net stop vss
Net stop swprv
regsvr32 ole32.dll
regsvr32 oleaut32.dll
regsvr32 vss_ps.dll
vssvc /register
regsvr32 /i swprv.dll
regsvr32 /i eventcls.dll
regsvr32 es.dll
regsvr32 stdprov.dll
regsvr32 vssui.dll
regsvr32 msxml.dll
regsvr32 msxml3.dll
regsvr32 msxml4.dll

Note The last command may not run successfully.

3. Rerun the converter.

Note : This article is not for use with Windows Vista, with Windows Server 2008, or with later operating systems. Starting with Windows Vista and with Windows Server 2008, Windows component installation is manifest based. If you try to manually register specific components, such as those that are described in this "Resolution" section, in the operating systems that are mentioned in this note, unexpected results may occur that may require reinstalling Windows to resolve. 

VMware vMotion error at 14% - Scene 2

Issue

While performing vMotion, the operation fails at 14% with the below error :

vMotion migration [-1062731490:1419235061251156] failed to create a connection with remote host : The ESX hosts failed to connect over the VMotion network
Migration [-1062731490:1419235061251156] failed to connect to remote host <Destination vMotion IP> from host : Network unreachable
The vMotion failed because the destination host did not receive data from the source host on the vMotion network. Please check your vMotion network settings and physical network configuration and ensure they are correct.

Resolution

I've already penned a post on VMware vMotion failure at 14%. This blog is an extended version of that post. If none of the steps mentioned in my previous post helped you, then you are in the right page.

Check whether vMotion is selected for multiple vmkernel NICs in ESXi host. !!!!

If yes, make only one NIC available for vMotion.