Controller The controller node runs the Identity service, Image service, management portions of Compute, management portion of Networking, various Networking agents, and the dashboard. It also includes supporting services such as an SQL database, message queue, and NTP. Optionally, the controller node runs portions of the Block Storage, Object Storage, Orchestration, and Telemetry services. The controller node requires a minimum of two network interfaces. --------------------------------------- Compute The compute node runs the hypervisor portion of Compute that operates instances. By default, Compute uses the KVM hypervisor. The compute node also runs a Networking service agent that connects instances to virtual networks and provides firewalling services to instances via security groups. You can deploy more than one compute node. Each node requires a minimum of two network interfaces. --------------------------------------- Block Storage The optional Block Storage node contains the disks that the Block Storage and Shared File System services provision for instances. For simplicity, service traffic between compute nodes and this node uses the management network. Production environments should implement a separate storage network to increase performance and security. You can deploy more than one block storage node. Each node requires a minimum of one network interface. --------------------------------------- Object Storage The optional Object Storage node contains the disks that the Object Storage service uses for storing accounts, containers, and objects. For simplicity, service traffic between compute nodes and this node uses the management network. Production environments should implement a separate storage network to increase performance and security. This service requires two nodes. Each node requires a minimum of one network interface. You can deploy more than two object storage nodes.
Let's quickly review just what a computing cloud is. Cloud technologies are built on existing technologies such as virtualization and clustering to virtualize hardware, software, storage, and networking resources into flexible units that are quickly allocated to meet demand. So rather than the old static model of dedicated hardware servers for various tasks, and static network and storage configurations, all of those formerly specialized devices are assimilated into a common resource pool. It's a more efficient use of hardware, and very fast to scale up or down according to demand. You can even configure self-service for users so they can grab whatever they need when they need it. Private clouds are hosted on your own premises, and there are public clouds like Amazon's EC2 and the Rackspace Cloud. You can combine private and public clouds in many useful ways. For example, keep your sensitive data locked away in your private cloud, and use a public cloud for sharing, testing, and extra non-sensitive storage. All computing resources are shareable in a cloud, and there are three basic service models: SaaS, software as a service PaaS, platform as a service IaaS, infrastructure as a service SaaS is centrally-hosted application software accessed by client software, with data typically kept on the server for access from any networked computer. Yes, just like in the olden client-server days, but the modern twist is to stuff everything through a Web browser. Using a Web browser as the client has its down sides, starting with HTTP, which was never designed for complex computing tasks, but by gosh we're making it haul water, chop wood, and dig ditches, and it's doing it cross-platform. SaaS is popular with software vendors because it reduces their support costs, gives them more control, and at long last supports that coveted grail of the monthly subscription model. It's nice for customers as well because they don't have to hassle with installation and maintenance. PaaS is a nice option for customers who want more control of their datacenter, but not all the headaches of system and network administration. An example of this is managed cloud Web hosting where the host takes care of hardware, operating systems, networking, load balancing, backups, and updates and patches. The customer manages the development and configuration of whatever software they want to use. It's like sitting down to a fully-configured datacenter and getting right to work. IaaS can be thought of as virtual bare hardware that the customer managers like a physical server, with control of all the software and configuration. You could also call it HaaS, hardware as a service.
Software that arbitrates and controls VM access to the actual underlying hardware. ------------------------------ A hypervisor or virtual machine monitor (VMM) is computer software, firmware, or hardware, that creates and runs virtual machines. A computer on which a hypervisor runs one or more virtual machines is called a host machine and each virtual machine is called a guest machine. The hypervisor presents the guest operating systems with a virtual operating platform and manages the execution of the guest operating systems. Multiple instances of a variety of operating systems may share the virtualized hardware resources: for example, Linux, Windows, and OS X instances can all run on a single physical x86 machine. This contrasts with operating-system-level virtualization, where all instances (usually called containers) must share a single kernel, though the guest operating systems can differ in user space, such as different Linux distributions with the same kernel. The term hypervisor is a variant of supervisor, a traditional term for the kernel of an operating system: the hypervisor is the supervisor of the supervisor, with hyper- used as a stronger variant of super-.[a] The term dates to circa 1970; in the earlier CP/CMS (1967) system the term Control Program was used instead. ------------------------------------------ A hypervisor is a function which abstracts -- isolates -- operating systems and applications from the underlying computer hardware. This abstraction allows the underlying host machine hardware to independently operate one or more virtual machines as guests, allowing multiple guest VMs to effectively share the system's physical compute resources, such as processor cycles, memory space, network bandwidth and so on. A hypervisor is sometimes also called a virtual machine monitor hypervisor Posted by: Margaret Rouse WhatIs.com Contributor(s): Stephen J. Bigelow This definition is part of our Essential Guide: Fine-tune your virtualization performance management skills Sponsored News ABC’s of VDI in 2016 –Dell Building a Private Cloud on Converged Infrastructure –Dell See More Vendor Resources Virtual Data Center E-Zine Volume 33: Time to Consider a Second Hypervisor? –SearchDataCenter.com Expert Strategies to Securing a Virtual Environment –SearchSecurity.com A hypervisor is a function which abstracts -- isolates -- operating systems and applications from the underlying computer hardware. This abstraction allows the underlying host machine hardware to independently operate one or more virtual machines as guests, allowing multiple guest VMs to effectively share the system's physical compute resources, such as processor cycles, memory space, network bandwidth and so on. A hypervisor is sometimes also called a virtual machine monitor. Download this free guide Download: Essential Guide to Choosing Virtualization Hardware Modern servers are shipping with massive amounts of memory, multiple network interface cards and support for solid-state storage. With all the options available, it's hard to know what you need. This complimentary guide on choosing the best hardware for virtualization can help. Hypervisors provide several benefits to the enterprise data center. First, the ability of a physical host system to run multiple guest VMs can vastly improve the utilization of the underlying hardware. Where physical (nonvirtualized) servers might only host one operating system and application, a hypervisor virtualizes the server, allowing the system to host multiple VM instances -- each running an independent operating system and application -- on the same physical system using far more of the system's available compute resources. VMs are also very mobile. The abstraction that takes place in a hypervisor also makes the VM independent of the underlying hardware. Traditional software can be tightly coupled to the underlying server hardware, meaning that moving the application to another server requires time-consuming and error-prone reinstallation and reconfiguration of the application. By comparison, a hypervisor makes the underlying hardware details irrelevant to the VMs. This allows any VMs to be moved or migrated between any local or remote virtualized servers -- with sufficient computing resources available -- almost at-will with effectively zero disruption to the VM; a feature often termed live migration. VMs are also logically isolated from each other -- even though they run on the same physical machine. In effect, a VM has no native knowledge or dependence on any other VMs. An error, crash or malware attack on one VM does not proliferate to other VMs on the same or other machines. This makes hypervisor technology extremely secure. Finally, VMs are easier to protect than traditional applications. A physical application typically needs to be first quiesced and then backed up using a time-consuming process that results in substantial downtime for the application. A VM is essentially little more than code operating in a server's memory space. Snapshot tools can quickly capture the content of that VM's memory space and save it to disk in moments -- usually without quiescing the application at all. Each snapshot captures a point-in-time image of the VM which can be quickly recalled to restore the VM on demand. Types of hypervisors Hypervisors are traditionally implemented as a software layer -- such as VMware vSphere or Microsoft Hyper-V -- but hypervisors can also be implemented as code embedded in a system's firmware. There are two principal types of hypervisor. Type 1 hypervisors are deployed directly atop the system's hardware without any underlying operating systems or other software. These are called "bare metal" hypervisors and are the most common and popular type of hypervisor for the enterprise data center. Examples include vSphere or Hyper-V. Type 2 hypervisors run as a software layer atop a host operating system and are usually called "hosted" hypervisors like VMware Player or Parallels Desktop. Hosted hypervisors are often found on endpoints like PCs. What are hypervisors used for? Hypervisors are important to any system administrator or system operator because virtualization adds a crucial layer of management and control over the data center and enterprise environment. Staff members not only need to understand how the respective hypervisor works, but also how to operate supporting functionality such as VM configuration, migration and snapshots. The role of a hypervisor is also expanding. For example, storage hypervisors are used to virtualize all of the storage resources in the environment to create centralized storage pools that administrators can provision -- without having to concern themselves with where the storage was physically located. Today, storage hypervisors are a key element of software-defined storage. Networks are also being virtualized with hypervisors, allowing networks and network devices to be created, changed, managed and destroyed entirely through software without ever touching physical network devices. As with storage, network virtualization is appearing in broader software-defined network or software-defined data center platforms.