Monday, September 17, 2012

VMware Technical Questions and Answers and Interview FAQ -Part3


21.    What products are available for Server Virtualization?

Bare Metal Hypervisor / Native / Type 1: VMware ESX Server

Microsoft Hyper-V Citrix/Xen Server

Hosted in an OS /

 Type2: VMware Server

Microsoft Virtual Server Parallels Server

22.    What products are available for desktop virtualization?

Host in an OS / Type 2 / intended for workstations: VMware Workstation

Microsoft Virtual PC Parallels Workstation VMware Fusion for Mac OS Parallels Desktop for Mac OS

23.  What is the difference between ESX Server and VMware Server?

While both ESX Server and VMware Server are server virtualization products, the difference is that VMware ESX installs and runs on the bare metal of a physical server where as VMware Server needs a base operating system. In other words, VMware ESX has a type 1 hypervisor where as VMware Server has a type 2 hypervisor.

You will obtain must better performance from ESX Server as it has much less overhead. ESX Server also has many features available such as VMFS, VMotion, VMHA, and DRS. On the other hand, ESX Server is also a commercial product that must be purchased where as VMware Server is a free product. VMware Server is an excellent option to choose to slowly migrate to server consolidation at a low cost. VMware Server is also an excellent way to learn about virtualization as well as a way to run multiple operating systems on your desktop PC, at no cost.

24. What is the difference between Hyper-V and Virtual Server?

Like the difference between ESX Server and VMware Server, Hyper-V and Virtual server have similar differences. Hyper-V is a type-1 hypervisor where Virtual Server is a type 2 hypervisor. Virtual Server requires that you first host a Windows operating system to load it.

Hyper-V is meant to be a higher performance commercial virtualization platform with a centralized management platform and 3rd party add-ons. Virtual Server, on the other hand, is a free virtualization platform meant for the desktop or for small-scale server virtualization solutions.




25. What is the difference between emulation, native virtualization, and paravirtualization?

Emulation is where software is used to simulate hardware for a guest operating system to run in. This has been used in the past but is difficult to do and offers low performance.

Native virtualization (or full virtualization) is where a type-2 hypervisor is used to partially allow access to the hardware and partially to simulate hardware in order to allow you to load a full operating system. This is used by emulation packages like VMware Server, Workstation, Virtual PC, and Virtual Server.

Paravirtualization is where the guest operating systems run on the hypervisor, allowing for higher performance and efficiency. For more technical information and videos on this topic, visit VMware’s Technology Preview for Transparent Virtualization. Examples of paravirtualization are Microsoft Hyper-V and VMware ESX Server.

26.What are the different types of virtualization?

Server Virtualization – consolidating multiple physical servers into virtual servers that run on a single physical server.

Application Virtualization – an application runs on another host from where it is installed in a variety of ways. It could be done by application streaming, desktop virtualization or VDI, or a VM package (like VMware ACE creates with a player). Microsoft Softgrid is an example of Application virtualization.

Presentation Virtualization – This is what Citrix Met frame (and the ICA protocol) as well as Microsoft Terminal Services (and RDP) are able to create. With presentation virtualization, an application actually runs on another host and all that you see on the client is the screen from where it is run.

Network Virtualization – with network virtualization, the network is “carved up” and can be used for multiple purposes such as running a protocol analyzer inside an Ethernet switch. Components of a virtual network could include NICs, switches, VLANs, network storage devices, virtual network containers, and network media.

Storage Virtualization – with storage virtualization, the disk/data storage for your data is consolidated to and managed by a virtual storage system. The servers connected to the storage system aren’t aware of where the data really is. Storage virtualization is sometimes described as “abstracting the logical storage from the physical storage.

27. Why do I care that VMware ESX uses the VMFS?

VMware’s VMFS was created just for VMware virtualization. VMFS is a high performance cluster file system allowing multiple systems to access the file system at the same time. VMFS is what gives you the necessary foundation to perform VMotion and VMHA. With VMFS you can dynamically increase a volume, support distributed journaling, and the addition of a virtual disk on the fly.

28. How do I backup my virtual guest operating systems?

There are multiple ways to backup your virtual guest operating systems. As long as your critical data is sent offsite and follows your backup rotation, you are doing well.

One option would be to run a a backup client inside each guest operating system, just like you do your physical servers.

If you are using a bare metal virtualization platform (like ESX Server), the greatest challenge is sometimes gaining access to your data. For example, with ESX Server, your data is stored inside ESX Server’s VMFS file system. That file system cannot be accessed by a typical Windows or Linux backup client. For that reason, there are specialized virtualization backup products like Vizioncore’s vRanger an EsXpress.

29. What are VMware VMotion & Storage VMotion (SVMotion)?

With VMotion, VM guests are able to move from one ESX Server to another with no downtime for the users. What is required is a shared SAN storage system between the ESX Servers and a VMotion license.

Storage VMotion (or SVMotion) is similar to VMotion in the sense that it moves VM guests without any downtime. However, what SVMotion also offers is the capability to move the storage for that guest at the same time that it moves the guest. Thus, you could move a VM guest from one ESX server’s local storage to another ESX server’s local storage with no downtime for the end users of that VM guest.

30.What is VMware HA?

One of the most amazing capabilities of VMware ESX is VMHA. With 2 ESX Servers, a SAN for shared storage, Virtual Center, and a VMHA license, if a single ESX Server fails, the virtual guests on that server will move over to the other server and restart, within seconds. This feature works regardless of the operating system used or if the applications support it.

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