Architecture and Benefits of VMware vSphere Virtualization

Architecture and Benefits of VMware vSphere Virtualization- Part - I

In today’s world many technocrats, DBAs, CIOs and CTOs are very concerned about the expenses bill on hardware procurements and also on the optimal , consolidated and cost-effective usage of the same.  I will try to get inside the problem with the help virtualization as a solution and try to build a series of blogs on virtualization (with special reference to vBlock and Oracle) . In this particular blog I will try to address the basic concepts of virtualization and its comparison with the traditional physical server architecture.

Virtualization Traditionally, operating systems and software run on a physical server. Many challenges exist in running a large number of physical servers in a typical datacenter. To run this type of infrastructure may not be efficient and cost effective in the long run. To plan and spend for the maintenance cost of this type of very large infrastructure (square footage, rack space, power, cooling, cabling, and server provisioning) are some of the problems that IT staff  and their managements are addressing on a daily basis.

Typically, there exists a one to one correspondence between a physical computer and the software that it runs. This relationship leaves most of the resources of the computers hugely idle and underutilized, leaving between only 5–15 percent (approx.) of physical server capacity in use. The cost of the space and power required to house, run and keep these systems cool can be expensive.

It is very tedious to provision physical servers as it is a time consuming process. In nonvirtualized environments time is required to procure new hardware, and get it installed in the datacenter, install and patch an operating system and finally install and configure the required applications on the same and that can take a huge time duration to get going. This process also includes many other tasks to integrate the system into the infrastructure. For example, configuring databases, servers, firewall rules, enabling switch ports and provisioning storage. Below figure shows us a basic landscape of virtualization.

Benefits The benefits of using the virtual Box vis-a-vis Physical box can be summed up in the following chart.

In physical environments, the OS is installed on the top of the physical hardware and while upgrading ,we need to ensure that the device drivers are in right version and installed properly as per the requirements and latest compatibility matrix. If there are incompatibilities, there may be some adverse implications in terms of business cost ,time and personnel.

Virtualizing these systems save on this cost because virtual machines are 100 percent software. The virtual machine is a set of files. A virtual machine uses standardized virtual device drivers. The hardware can be upgraded without change to the virtual machine.

Architecture The difference between the Physical and the virtual architecture can be depicted in the below diagram:-

The graphics shown above illustrate the differences between a virtualized and a nonvirtualized host. In traditional architectures, the operating system interacts directly with the installed hardware. It schedules processes to run, allocates memory to applications, sends and receives data on network interfaces and reads from and writes to attached storage devices. In comparison, a virtualized host interacts with installed hardware through a thin layer of software called the virtualization layer or hypervisor. The hypervisor provides physical hardware resources dynamically to virtual machines as needed to support the operation of the virtual machines. The hypervisor allows virtual machines to operate with a degree of independence from the underlying physical hardware. For example, a virtual machine can be moved from one physical host to another. Also, its virtual disks can be moved from one type of storage to another without affecting the functioning of the virtual machine.

Virtualization is the panacea for many problems that related to the CPU, memory, and networking and resources bottlenecks. Virtualization is a technology that decouples physical hardware from a computer operating system and allows us to consolidate and run multiple workloads as virtual machines on a single computer. In short ,a virtual machine is a computer that is created by software that enables us to use all the computer resources in a shared manner and enables us to run  like a physical computer which runs an operating system and applications. Each virtual machine contains its own virtual hardware, including a virtual CPU, memory, hard disk, and network interface card, which look like physical hardware to the operating systems and applications.

Scope for Virtualization

There are multiple benefits/scope for virtualization as shown below :-

• CPU Virtualization
• Memory Virtualization
• Networking Virtualization
• File System Virtualization
• Server resources sharing or Virtualization

In the next blog I will discuss the architecture of vSphere and its allied features in greater detail. In the future blogs, I will try to take take a deep dive into the various aspects of virtualization with special reference to vSphere and oracle. Gradually I will highlight why Oracle should be used in  virtualized environment like vSphere which leverages the performance of Oracle Database and also reduces the TCO of the DB in terms of licensing costs.

Further Suggested Readings : Best Practices for Virtualizing Your Oracle Database – Datastores

 

Architecture and Benefits of VMware vSphere Virtualization- Part - II

In my last blog, I discussed about the basics of Virtualization. In this blog, I will discuss the components, features and benefits of vSphere.

Today’s IT leaders have to balance the often-competing demands of delivering greater flexibility, availability and responsiveness to change, with the need to manage costs. To that end, trends in the datacenter point towards the growth in the use of virtualized servers exceeding that of physical servers. Here VMWare’s vSphere plays an important role. VMware vSphere is the brand name for VMware's suite of virtualization products. Before 2009, VMware vSphere was known as VMware Infrastructure.

VMware® vSphere® is an infrastructure virtualization suite that provides virtualization, management, resource optimization, application availability, and operational automation capabilities in an integrated package. vSphere virtualizes and aggregates the underlying physical hardware resources across multiple systems and provides pools of virtual resources to the datacenter. In addition, vSphere provides a set of distributed services that enable detailed, policy-driven resource allocation, high availability, and scalability of the entire virtual datacenter.

VMware vSphere, which is a necessary component of the vCloud Suite for cloud computing, includes

• VMware ESXi -  abstracts processor, memory, storage, and other resources into multiple virtual machines (VMs).
• VMware vCenter Server - central control point for data center services such as access control, performance monitoring and alarm management.
• VMware vSphere Client - allows users to remotely connect to ESXi or vCenter Server from any Windows PC.
• VMware vSphere Web Client - allows users to remotely connect to vCenter Server from a variety of Web browsers and operating systems (OSes).
• VMware vSphere SDKs - provides interfaces for accessing vSphere components.
• vSphere Virtual Machine File System (VMFS) - provides a high performance cluster file system for ESXi VMs.
• vSphere Virtual SMP - allows a single virtual machine to use multiple physical processors at the same time.
• vSphere vMotion - allows live migration for powered-on virtual machines in the same data center.
• vSphere Storage vMotion -  allows virtual disks or configuration files to be moved to a new data store while a VM is running.
• vSphere High Availability (HA) - allows virtual machines to be restarted on other available servers.
• vSphere Distributed Resource Scheduler (DRS) - divides and balances computing capacity for VMs dynamically across collections of hardware resources.
• vSphere Storage DRS - divides and balances storage capacity and I/O across collections of data stores dynamically.
• vSphere Fault Tolerance - provides continuous availability.
• vSphere Distributed Switch (VDS) -  allows VMs to maintain network configurations as the VMs migrate across multiple hosts.
• Host Profiles - provides a way to create user-defined configuration policies.

VMWare vSphere undergoes periodic revisions and updates to add features, modifications to the application program interface (API) and changes to the ESXi Shell. VMware offers vSphere in several kits (Essentials and Essentials Plus) and editions (Standard, Enterprise and Enterprise Plus.)

Some Salient Features of  VMWARE vSphere

Below are some features of the vSphere which takes the product apart in the virtualization domain.

• vSphere as a Software Define Data Center

The software defined datacenter is considered to be the foundation of cloud computing. The software defined datacenter deploys virtual datacenters with isolated computing, storage, networking and security resources faster than the traditional hardware based datacenter. vSphere is critical to the success of the software defined datacenter because it provides the hardware and networking abstraction and resource pooling necessary for the datacenter to deploy. Below diagram provides us some illustration:

• vSphere fits into Cloud Computing

The consolidation and rapid virtual machine provisioning results in a high-level of server use and reuse that enables an effective use of capital equipment. When coupled with technologies such as virtual machine migration, high availability, integrated data protection and centralized management it is easy to see how vSphere 5 is the clear choice for a cloud computing platform.

• Offers protection at every level with the allied tools of VMWare

At every level of the datacenter, from individual components all the way up to the entire site, VMware® vSphere® 5.x provides protection against both planned and unplanned downtime. All these features combine to provide greater availability to all supported operating systems and applications.Many methods ensure highly availability in a virtualized environment. vSphere 5.x uses technologies like the following to ensure that virtual machines running in the environment remain available:

• Virtual machine migration
• Multiple I/O adapter paths
• Virtual machine load balancing
• Fault tolerance
• Disaster recovery tools

There are myriads of other great features which require greater attention and worth mentioning. I will try to address all those in my future blogs.

Architecture and Benefits of VMware vSphere Virtualization- Part – III

In the previous blog, I talked about different features of VMware vSphere. In this blog, I would like to discuss a couple of features of vSphere as below :-

• Raw Device Mapping (RDM)
• vMotion Migration

 
Raw Device Mapping (RDM):- Introduced with ESX Server 2.5, raw device mapping allows a special file in a VMFS volume to act as a proxy for a raw device.

An RDM is a file stored in a VMFS volume that acts as a proxy for a raw physical device.Instead of storing virtual machine data in a virtual disk file stored on a VMFS datastore, we can store the guest operating system data directly on a raw LUN. Storing the data this way is useful if we are running applications in our virtual machines that must know the physical characteristics of the storage device. And mapping a raw LUN allows us to use existing SAN commands to manage storage for the disk. The mapping file contains metadata used to manage and redirect disk accesses to the physical device. The mapping file gives us some of the advantages of a virtual disk in the VMFS file system, while keeping some advantages of direct access to physical device characteristics. In effect, it merges VMFS manageability with raw device access.

An RDM is recommended when a virtual machine must interact with a real disk on the SAN. This condition is the case when we make disk array snapshots or have a large amount of data that we do not want to move onto a virtual disk as part of a physical to virtual conversion.

RDM can be used in the following scenario:-

• As a backup drive only.
• When VMFS virtual disk would become too large.
• Utilize native SAN tools – such as SAN snapshots
• Disaster Recovery – Connect RDM to another physical host
• vMotion activity à VM is registered to destination host

   
In below diagram we can observe that

• RDM is enabled us to store virtual machine data directly on a number of LUNs.
• The mapping file is stored on a VMware vSphere VMFS datastore that points to the raw LUN.

 

vMotion Migration:- VMware® VMotion™ enables the live migrationof running virtual machines from one physical server to another with zero downtime, continuous service availability, and complete transaction integrity. VMotion is a key enabling technology for creating the dynamic, automated, and self-optimizing datacenter.

vMotion migrates running virtual machines from one server to another with no disruption or downtime. vMotion enables VMware vSphere® Distributed Resource SchedulerTM (DRS) to migrate running virtual machines from one host to another to balance the load.

With vMotion, the entire state of the virtual machine is moved from one host to another while the data storage remains in the same datastore.

The state information includes the current memory content and all the information that defines and identifies the virtual machine. The memory content includes transaction data and whatever bits of the operating system and applications are in memory. The definition and identification information stored in the state includes all the data that maps to the virtual machine hardware elements, such as:

• BIOS
• Devices
• CPU
• MAC addresses for the Ethernet cards

   
The source and destination host must meet the below requirements for a vMotion migration to be successful

• SAN visibility of virtual disks.
• Gigabit Ethernet (or greater) interconnection
• Consistent network configuration, both physical and virtual
• Source and destination server CPUs from the same compatibility group

  The VM requirements for vMotion migration are the following :-

• RDM must be accessible to the destination host if the former is used by VM.
• vMotion must be able to create a swap file if the VM’s swap file is not accessible to the destination host.
• A VM must not have CPU affinity configured.
• A VM must not have connection to an internal standard virtual switch or to a virtual device like CD-ROM or floppy drive with a local image mounted.

   

Working Mechanism of vMotion Migration

Live migration of a virtual machine from one physical server to another with VMware VMotion is enabled by three underlying technologies.

First, the entire state of a virtual machine is encapsulated by a set of files stored on shared storage such as Fibre Channel or iSCSI Storage Area Network (SAN) or Network Attached Storage (NAS). VMware vStorage VMFS allows multiple
installations of VMware ESX® to access the same virtual machine files concurrently.

Second, the active memory and precise execution state of the virtual machine is rapidly transferred over a high speed network, allowing the virtual machine to instantaneously switch from running on the source ESX host to the destination ESX host. VMotion keeps the transfer period imperceptible to users by keeping track of on-going memory transactions in a bitmap. Once the entire memory and system state has been copied over to the target ESX host, VMotion suspends the source virtual machine, copies the bitmap to the target ESX host, and resumes the virtual machine on the target ESX host. This entire process takes less than two seconds on a Gigabit Ethernet network.

Third, the networks being used by the virtual machine are also
virtualized by the underlying ESX host, ensuring that even after the migration, the virtual machine network identity and network connections are preserved. VMotion manages the virtual MAC address as part of the process. Once the destination machine is activated, VMotion pings the network router to ensure that it is aware of the new physical location of the virtual MAC address. Let us now understand the technical implication with below diagram:-

In the above diagram, the source host is esx01 and the target host is esx02. The source host and the target host have access to the shared datastore holding the virtual machine’s files.

A vMotion migration consists of the following steps:

1. The virtual machine’s memory state is copied over the vMotion network from the source host to the target host. Users continue to access the virtual machine and, potentially, update pages in memory. A list of modified pages in memory is kept in a memory bitmap on the source host.
2. After most of the virtual machine’s memory is copied from the source host to the target host, the virtual machine is quiesced. No additional activity occurs on the virtual machine. In the quiesce period, vMotion transfers the virtual machine device state and memory bitmap to the destination host.
3. Immediately after the virtual machine is quiesced on the source host, the virtual machine is initialized and starts running on the target host. A Reverse Address Resolution Protocol (RARP) request notifies the subnet that virtual machine A’s MAC address is now on a new switch port.
4. Users access the virtual machine on the target host instead of the source host.
5. The memory pages that the virtual machine was using on the source host are marked as free.

  
Benefits of using vMotion Migration

• Improve availability by conducting maintenance without disrupting business operations
• Move virtual machines within server resource pools to continuously align the allocation of resources to business priorities

In the next blog, I will try to discuss some more features of vSphere.