Wednesday, September 19, 2012

Vmware ,Vsphere,ESX Interview Frequently Asked Questions and

Admission Control Policy

Important Interview Question :-

what is admission control in ESX?

Admission Control Policy VMware ESX Server uses an admission control policy to ensure that sufficient unreserved memory and swap space are available before powering on a virtual machine. Memory must be reserved for the virtual machine's guaranteed minimum size; additional overhead memory is required for virtualization. Thus the total required for each virtual machine is the specified minimum plus overhead.

The overhead memory size is determined automatically; it is typically 54MB for a single virtual CPU virtual machine, and 64MB for a dual-virtual CPU SMP virtual machine. Additional overhead memory is reserved for virtual machines larger than 512MB.

Swap space must be reserved on disk for the remaining virtual machine memory — that is the difference between the maximum and minimum settings. This swap reservation is required to ensure the system is able to preserve virtual machine memory under any circumstances. In practice, only a small fraction of the swap space may actually be used.

Similarly, while memory reservations are used for admission control, actual memory allocations vary dynamically, and unused reservations are not wasted.

The amount of swap space configured for the system limits the maximum level of overcommitment. A default swap file size equal to the physical memory size of the computer is recommended in order to support a reasonable 2x level of memory overcommitment. You may configure larger or smaller swap files or add additional swap files.

If you do not configure a swap file, memory may not be over committed. You may configure the swap file using the VMware Management Interface (Swap Configuration in the Options page) or from the service console using the vmkfstools command.

You can create additional swap files using the vmkfstools command. You should consider adding additional swap files if you want to run additional virtual machines but you're unable to do so because of the lack of swap space. See Using vmkfstools.

1) Can we use EMC PowerPath together with VMware NMP (Native Multi-pathing Plug-in) ?

It is not recommended to use both at the same time, we usually either use PowerPath or VMware NMP. Refer to "EMC PowerPath VE With VSphere" documentation for more details.

2) Can we use VMware Update Manager (VUM) to schedule upgrading of VMware tools on the VMs to meet latest ESX hardware version ?

Yes, this is possible with VMware Update Manager 4. We do not need to create a new baseline, there's a default baseline that does this task.

3) Does Storage Vmotion use the Service Console to migrate running VMs live from one storage to another storage ?

Storage VMotion migrates VM via the Service Console network, this means that there's no additional burden on the other Virtual Machine connection network.

4) Can we implement VMware Fault Tolerance on a VM with an existing VMware Snapshot on the VM ?

No, VMware FT does not support VM with existing snapshots. We have to merge or discard the snapshot before enabling VMware FT to protect that VM.

5) What is the protocol used by vCenter Linked Mode to link to other Virtual Center Servers ? 

vCenter Management Server 4 uses LDAP via port 386 by default.

6) Does VMware supports installation of vCenter Server 4 on Windows Server 2008 R2 operating system platform ?

No, Windows Server 2008 R2 is not a supported platform for installing vCenter Server 4. Refer to "vSphere Compatibility Matrix" for details.

7) Is it possible to configure both thin provisioned virtual disk and thick provision virtual disk n a single VM, thus, creation of a VM with multiple virtual disks which have different provisioned modes virtual disk ?

Yes, this is possible.

8) When deploying thin provisioned virtual disk for VM, the virtual disk is expand on demand which creates many fragments which could be scattered across our datestore, what's the way to defrag a VM with thin provisioned virtual disk ?

When performing Storage Vmotion migrating the VM to a different LUN and migrating the VM back to original datastore, the VM's file will be fragmented.

9) During Scripted Installation of ESX Server 4, is it possible create local directory on the host and run scripts to install third party utilities from other vendors such as HP or Dell ?

Yes, it is possible to create a local directory to load packages then configure scripts to run pre or post installation of ESX Server. Refer to "Scripted Installation of ESX" for more information.

10) What's the major different between virtual network adapter E1000 and VMXNET3 ?

VMXNET3 is the third generation of paravirtual network adapter by VMware. Includes features such as MSI/MSI-X support, Receive Side Scaling, IPv6 checksum and TCP Segmentation Offloading (TSO) over IPv6, VLAN off-loading and Large TX/RX ring sizes. Refer to "vSphere Networking" guide and "E1000 and VMXNET3" discussion for more details.

11) Are we able to configure vCenter Server Heartbeat to keep replication and synchonization while disabling automatic failover and enabling only the option for a manual switch over ?

No, that is not possible with current version of vCenter Server Heartbeat.

12) If the local Windows OS running vCenter Server Heartbeat restarts after applying a security patch, will the Primary vCenter Server trigger a failover to the Secondary vCenter Server ?
As the default ping for the channel network is 3 pings with 20 seconds interval between each ping, the failover will occur and Secondary vCenter Server will take control and start protected services. However, we are able to configure the ping intervals in the vCenter Server Heartbeat manage server console.

13) Can we import host profiles created on our master vCenter Server located in our main datecenter to the vCenter Servers running in remote sites or branch offices ?

Yes, vCenter host profile configuration allows us to import host profiles created in virtual machine profile format .vpf into existing vCenter Servers that we wish to apply the host profiles.

14) Is it possible to configure a schedule task to stage ESX Server patching with VMware Update Manager ?
No, this is not possible with the current version of VMware Update Manager 4.

15) When migrating VMs with Storage VMotion, could we choose different datastore LUNs if our single VM has multiple virtual disks ?
Yes, when performing Storage Vmotion of a running VM live from one storage to another storage, at the screen when we are prompted to select datastore, we could click on "advanced" tab to select different datastores for our virtual disks.

16) Does vCenter Server Heartbeat works across LAN and WAN ?

Yes, it works both across LAN and WAN. Refer to "vCenter Server Heartbeat Reference Guide" for more details.

17) What's the main benefit of deploying ESXi 4.x Servers as compared to ESX 4 Servers in a datacenter production environment ?

There's significantly less patches required for an ESXi Server as compared to ESX Server. As ESXi does not have a service console, it is relatively more secure and less vulnerable to attacks.

18) Is it advisable to run anti virus software on the Service Console on ESX Servers in production environment ?

Running anti virus softwares in Service Console will generally take up resources which might affect performance of the ESX Server as the anti virus software requires resources to run.

19) In terms of hardening the ESX Server from a security aspect, what's the solution for managing root accounts on ESX Server hosts ?
We could restrict root user account logins and password only to datacenter administrators. We could than create linux user accounts inside Service Console and then enable sudo permissions to grant these users shell access. We could also join ESX Server to Active Directory authentication.

20) Is there a new VMFS version with VMware vSphere ?

No, vSphere is still running on VMFS3 version. However, there is a change in virtual machine hardware to version 7.

21) What's the maximum number of vCenter Servers we can configured in a linked mode ?

We can configure a total of 10 vCenter Servers in a vCenter Server linked mode. vCenter linked mode can manage up to 1000 ESX/ESXi Servers and 10000 virtual machines across 10 vCenter Servers in a single console.

22) What's the main functions and capabilities when deploying vCenter Server linked mode ? 

vCenter Server linked mode gives administrators a single pane of glass view, it allows administrators to share global roles and licenses across vCenter Servers.

23) What's the rollback option tab when configuring vCenter Server Heartbeat ?

As vCenter Server Heartbeat uses Microsoft Virtual Shadow Copy Service (VSS) we could configure a rollback. Refer to help guide on the local vCenter Server after installation and configuration of vCenter Server Heartbeat for details.

24) What are the supported Microsoft SQL version that can be protected by vCenter Server Heartbeat 5.5 update 1 ?

vCenter Server Heartbeat is currently able to protects only Microsoft SQL Server 2005 SP1-SP3 and Microsoft SQL Server 2008 versions.

25) Can we use vCenter Server 4 to manage legacy ESX 3.x and 2.x Servers ?

Yes, vCenter Server 4 can only manage legacy ESX Servers if we configure connectivity to an existing flexnet license server as vCenter Server 4 does not manage the licenses for legacy host directly.

26) After joining ESX Servers to Active Directory domain, can we use distribution groups instead of user accounts ?
VMware does not support the add of AD groups but it does support the adding of individual users and PAM module. Refer to "ESX Authentication AD"

27) Will vCenter Server Heartbeat works together with vCenter Linked Mode ?
Yes, vCenter Server Heartbeat and vCenter linked mode is compatible with the most current version update 2. Adam components will be replicated active and passive, therefore, full functionality is available when switch to target mode. Refer to "forum discussion" for more details.

28) Does vSphere 4 supports Microsoft Clustering VMs whose file resides on iSCSI LUN ?
No, this version of vSphere 4 is not compatible with iSCSI SAN for MSCS configuration. Refer to "Setup for Failover Clustering and MSCS" for more details.

29) When running resxtop command in vMA to view performance output, how do I view only VMs and not other worlds ?
After entering the resxtop command, we can enter "V" which will output displaying only VMs on that specific ESX Server.

30) If we set a memory limit of a VM to 400 MB and avaliable memory to 512 MB, what will happen after the VM reaches the limit ?
Based on the POC done in the class, the ballooning vmmemctl kicks in after the VM hits the 400MB limit. Thus, the remaining 112 MB of memory is not used.

31) Can we create a vmdk greater than 256 GB when configuring a block size of 1MB ?

No this is not possible, we will have to increase the block size before the vmdk size will be increased. For example, a block size of 2MB will allow us to create a 512GB vmdk and a block size of 4MB will allow us to create a vmdk that's 1024GB. Refer to "Forum discussion" for more details.

32) Where can I create the session file within the vMA ?
Session file creation can be found within the vMA when we access $ cd /usr/lib/vmware-vcli/apps/session

33) Does vCLI supports running on Linux and Windows OS ?

Yes, vCLI is supported and can be run from both Windows and Linux OS.

34) When can we use explicit failover on a vSwitch ?

We can select "use explicit failover" when we want vSwitch to always use the highest order uplink from the list of Active adapters which passes failover detection criteria such as link state only and beacon probing. Refer to "virtual switch policies" for more details.

35) What is the difference between consumed memory and active memory ?

Consumed memory is when there is no contention and active memory refers to the memory used when there is contention.
VMware View Frequently Asked Questions

Q1) What is the difference between desktop recomposition and desktop refresh ?

Desktop recomposition is use to update changes such as application updates, patches, service packs or even Vista upgrades to the source image. Desktop refresh is returning the image back to it's original state when you first deployed it.
2) During installation of View Connection Server, installation halted due to IIS using port 80, what should I do ?

There are 2 options, either you can stop the IIS service on the Windows OS you are installing the View Connection Server or you can change the port from 80 to 8000. This is because the installation requires the use of port 80.

3) If I have an SQL Server Application running in my 6gb VM and I decide to check it out, will the application be checkout as well ?
Yes, View client with offline desktop will checkout the entire VM including everything inside so that your mobile users can use their VM offline even without network connectivity.

4) What is the recommendation to protect VMware View Connection Server to ensure high avaliability ?

The way to build high availability is to configure replica View connection servers, the sessions information is replicated between View connection servers using ADAM.

5) If the user were to checkout an offline desktop and the online equavilent were to get patched by administrators, when the users update their offline desktop or run the backup will their offline desktops receive the patches as well ?

Update will not be possible as this kind of operations is not available.

6) Is the link clone technology used in VMware View Composer similar to the one used in VMware Lab Manager ?

No. When using VMware View Composer link clone technology to create multiple desktops or pool of desktops
using the Automated Desktop Delivery option, the virtual machines being created are reflected in the Virtual Center Server via VI Client.

7) Besides integration with AD, what other directory services does VMware View integrate with ?

As of present, it is only able to integrate with AD and no other services.

8) Is there a way to enhance the security level on my View Connection Server ?

Yes. We can integrate VMware View Connection Server with RSA Secur ID.

9) Name me a key difference between VMware View and Citrix Xen desktop virtualization ?

Citrix is a forward looking technology which supports W2k3 OS and above. Whereas, VMware View gives users the flexibility of looking at a wider range of OS ranging from legacy OS to the latest OS available in the market.

10) Does VMware View's VMs support printer drivers and usb devices on the client ?

Yes. There is support for all printer drivers as it is using virtual drivers and usb devices on the VMs are also supported.

11) What is the benefit of using VMware ThinApp for packaging an application ?

It packs the application into an exe file which means you do not have to install the application into your user's system drive. The exe file can be run from any location including network shares, usb drives and cd roms. This helps save space and increases performance of user's desktop.

12) What is the default maximum caching time for offline desktop ?

The default maximum cache life is 7 days but we can choose to change this number to a higher number of days. This setting can be changed when you login to your view administrator via browser -> desktops and pools -> global policies -> offline desktop policies -> edit -> change the number of days

13) What is the purpose of the cache lifetime setting for the offline desktop ?

The data on each offline system is encrypted and has a cache lifetime controlled through policy, if the client loses contact with the View Connection Server, the cache lifetime is the period in which the user can continue to use the desktop before they are refused access; this countdown is reset once the connection is re-established.

14) Does Offline Desktop support tunneled or non tunneled communications ?
Offline Desktop supports tunneled or nonatunneled communications for LANabased data transfers. When tunneling is enabled, all traffic is routed through the View Connection Server.

When tunneling is not enabled, data transfers take place directly between the online desktop host system and the offline client.

15) Is it true that by passing the tunnel increases the data transfer speed ?
Yes, but do note that bypassing the tunnel and using an unencrypted connection increases data transfer speed at the expense of secure data communication. The encryption setting has no effect on the offline data, which is always encrypted on the client system.

16) When users are logon to their Virtual Machines via View Client, when they wish to end the session, should they choose "disconnect" or "disconnect and log off" option ?

The first option is Disconnect. With Disconnect, the user remains logged on. Any programs that the user is running continue to run and no other users (except for an Administrator) can connect to this desktop. If an administrator chooses, they may log into the desktop, but will automatically log the user out and force any programs the user was running to end. The second option is Disconnect and Log off. This option allows the user to log off and it allows other users to access this desktop.

17) What is estimated size of a linked clone system disk ?

For a 20GB system disk with OS and application, the estimated linked clone size would be 100mb, this size will typically grow to the size of the system disk and then a refresh would return it back to the original size. Refer to "Introduction To View" for more details.

18) How does VMware charge for VMware View licenses ?

Licenses are based on per concurrent connection user. Refer to "View 4 licensing" for more information.

19) Can we intergrate VMware View Connection Server with 3rd party Secure Access boxes ?

Yes, it is possible for such setup. Refer to "Juniper SA box with Vmware View" for secure access.

20) Does the View Security Servers in the DMZ zone do their own load balancing ?

VMware View does not provide load balancing features, we have to rely on 3rd party load balancing softwares such as NLB.
21) Does the virtual desktops support serial com ports ?

Yes, virtual desktops support serial, parallel, HID and usb ports. Refer to "View Peripherals" for more information.
22) Can VMware View client be installed on Linux OS ?

Yes, View Client can be installed on Linux OS. Refer to "View Client Compatibility Guide" for more information.
23) Does the ADAM database scheme change ?

No, the schema does not change.

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