30th September, 2020
Welcome to VMware vSphere Tutorials. The objective of these tutorials is to provide an in-depth understanding of VMware vSphere.
In addition to free VMware vSphere Tutorials, we will cover common interview questions, issues and how to’s of VMware vSphere.
VMware vSphere leverages the power of virtualization to transform datacenters into simplified cloud computing infrastructures and enables IT organizations to deliver flexible and reliable IT services. VMware vSphere virtualizes and aggregates the underlying physical hardware resources across multiple systems and provides pools of virtual resources to the datacenter.
As a cloud operating system, VMware vSphere manages large collections of infrastructure (such as CPUs, storage, and networking) as a seamless and dynamic operating environment, and also manages the complexity of a data center.
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The following component layers make up VMware vSphere:
Infrastructure Services are the set of services provided to abstract, aggregate, and allocate hardware or infrastructure resources. Infrastructure Services can be categorized into:
-VMware vCompute—the VMware capabilities that abstract away from underlying disparate server resources. vCompute services aggregate these resources across many discrete servers and assign them to applications.
-VMware vStorage—the set of technologies that enables the most efficient use and management of storage in virtual environments.
-VMware vNetwork—the set of technologies that simplify and enhance networking in virtual environments.
Application Services are the set of services provided to ensure availability, security, and scalability for applications. Examples include HA and Fault Tolerance.
VMware vCenter Server provides a single point of control of the datacenter. It provides essential datacenter services such as access control, performance monitoring, and configuration.
Users can access the VMware vSphere datacenter through clients such as the vSphere Client or Web Access through a Web browser
VMware vCenter Server
VMware vCenter Server provides centralized management for datacenters. vCenter Server aggregates physical resources from multiple ESX/ESXi hosts and presents a central collection of simple and flexible resources for the system administrator to the provision to virtual machines in the virtual environment. vCenter Server components are user access control, core services, distributed services, plug-ins, and various interfaces.
The User Access Control component allows the system administrator to create and manage different levels of access to vCenter Server for different classes of users. For example, a user class might manage and configure the physical virtualization server hardware in the datacenter. Another user class might only manage virtual resources within a particular resource pool in the virtual machine cluster.
vCenter Server interfaces integrate vCenter Server with third-party products and applications.
vCenter Server has four key interfaces:
Interfaces with the vCenter Server agent to manage each physical server in the datacenter.
Interfaces with VMware management clients and third-party solutions.
Connects to Oracle, Microsoft SQL Server, or IBM DB2 to store information, such as virtual machine configurations, host configurations, resources and virtual machine inventory, performance statistics, events, alarms, user permissions, and roles.
Connects to Active Directory to obtain user access control information.
The VMware vSphere storage architecture consists of layers of abstraction that hide and manage the complexity and differences among physical storage subsystems.
To the applications and guest operating systems inside each virtual machine, the storage subsystem appears as a virtual SCSI controller connected to one or more virtual SCSI disks as shown in Figure. These controllers are the only types of SCSI controllers that a virtual machine can see and access and include BusLogic Parallel, LSI Logic Parallel, LSI Logic SAS, and VMware Paravirtual.
The virtual SCSI disks are provisioned from datastore elements in the datacenter. A datastore is like a storage appliance that delivers storage space for virtual machines across multiple physical hosts. The datastore abstraction is a model that assigns storage space to virtual machines while insulating the guest from the complexity of the underlying physical storage technology. The guest virtual machine is not exposed to Fibre Channel SAN, iSCSI SAN, direct-attached storage, and NAS. Each virtual machine is stored as a set of files in a directory in the datastore. The disk storage associated with each virtual guest is a set of files within the guest's directory. You can operate on the guest disk storage as an ordinary file. It can be copied, moved, or backed up. New virtual disks can be added to a virtual machine without powering it down. In that case, a virtual disk file (.vmdk) is created in VMFS to provide new storage for the added virtual disk or an existing virtual disk file is associated with a virtual machine. Each datastore is a physical VMFS volume on a storage device. NAS datastores are an NFS volume with VMFS characteristics. Datastores can span multiple physical storage subsystems, a single VMFS volume can contain one or more LUNs from a local SCSI disk array on a physical host, a Fibre Channel SAN disk farm, or iSCSI SAN disk farm. New LUNs added to any of the physical storage subsystems are detected and made available to all existing or new datastores. Storage capacity on a previously created datastore can be extended without powering down physical hosts or storage subsystems. If any of the LUNs within a VMFS volume fails or becomes unavailable, only virtual machines that touch that LUN are affected. An exception is the LUN that has the first extent of the spanned volume. All other virtual machines with virtual disks residing in other LUNs continue to function as normal.
VMFS is a clustered file system that leverages shared storage to allow multiple physical hosts to read and write to the same storage simultaneously. VMFS provides on-disk locking to ensure that the same virtual machine is not powered on by multiple servers at the same time. If a physical host fails, the on-disk lock for each virtual machine is released so that virtual machines can be restarted on other physical hosts.
VMFS also features failure consistency and recovery mechanisms, such as distributed journaling, a failure consistent virtual machine I/O path, and machine state snapshots. These mechanisms can aid quick identification of the cause and recovery from the virtual machine, physical host, and storage subsystem failures.
VMFS also supports raw device mapping (RDM). RDM provides a mechanism for a virtual machine to have direct access to a LUN on the physical storage subsystem (Fibre Channel or iSCSI only). RDM is useful for supporting two typical types of applications:
-SAN snapshot or other layered applications that run in the virtual machines. RDM better enables scalable backup offloading systems using features inherent to the SAN.
-Microsoft Clustering Services (MSCS) spanning physical hosts and using virtual-to-virtual clusters as well as physical-to-virtual clusters. Cluster data and quorum disks must be configured as RDMs rather than files on a shared VMFS.
An RDM is a symbolic link from a VMFS volume to a raw LUN. The mapping makes LUNs appear as files in a VMFS volume. The mapping file, not the raw LUN, is referenced in the virtual machine configuration.
When a LUN is opened for access, the mapping file is read to obtain the reference to the raw LUN. Thereafter, reads and writes go directly to the raw LUN rather than going through the mapping file.
The VMware vSphere storage architecture enables VMware Consolidated Backup. Consolidated Backup provides a centralized facility for LAN-free backup of virtual machines.
Consolidated Backup works in conjunction with a third-party backup agent residing on a separate backup proxy server (not on the server running ESX/ESXi) but does not require an agent inside the virtual machines.
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