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In computer networking, a bare-metal server is a physical computer server that is used by one consumer, or tenant, only. [1] Each server offered for rental is a distinct physical piece of hardware that is a functional server on its own. They are not virtual servers running in multiple pieces of shared hardware.
The term is used for distinguishing between servers that can host multiple tenants and which use virtualisation and cloud hosting. [2] Unlike bare-metal servers, cloud servers are shared between multiple tenants. Each bare-metal server may run any amount of work for a user, or have multiple simultaneous users, but they are dedicated entirely to the entity who is renting them.
Hypervisors provide some isolation between tenants but there can still be a noisy neighbour effect. [3] If a physical server is multi-tenanted, peaks of load from one tenant may consume enough machine resources to temporarily affect other tenants. As the tenants are otherwise isolated, it is also hard to manage or load balance this. Bare-metal servers, and single tenancy, can avoid this. [2] In addition, hypervisors provide weaker isolation and are much more risky from a security point-of-view compared to using separate machines. Attackers have always found vulnerabilities in the isolation software (such as hypervisors), covert channels are impractical to counter without physically separate machines, and shared hardware is vulnerable to defects in hardware protection mechanisms such as Rowhammer, Spectre, and Meltdown. [4] As, once again, server costs are dropping as a proportion of total cost of ownership against their administration overhead, the classic solution of 'throwing hardware at the problem' becomes viable again.
Bare-metal cloud servers do not run a hypervisor, are not virtualised -- but can still be delivered via a cloud-like service model.
Infrastructure as a service, particularly through infrastructure as code, offers many advantages to make hosting conveniently manageable. Combining the features of both cloud hosting, and bare-metal servers, offers most of these, whilst still conveying the performance advantages. [5] These cloud offerings are also called Bare-Metal-as-a-Service (BMaaS).
Some bare-metal cloud servers may run a hypervisor or containers, e.g., to simplify maintenance or provide additional layers of isolation. [4]
Note that the distinction between these services and the traditional dedicated server offerings is the user's ability to provision infrastructures composed out of multiple servers, a complex network and storage setup rather than servers in isolation.
Both commercial and open-source platforms exist enabling companies to build their own private bare-Metal private clouds.
BMaaS software typically takes over the lifecycle management of the equipment in a datacenter (compute, storage and network Switches, firewalls, load balancers and others). It enables datacenter operators to offload much of the manual work typically associated with deploying hardware. It also reduces waste by simplifying reuse and increases security by implementing automatic cleanup and automatic segmentation between tenants at the network level. Increasingly BMaaS software is used internally to reduce the costs associated with lifecycle management of equipment for enterprises with large fleets of servers. [6]
BMaaS software aims to simplify hardware management and enable its as-a-service consumption. It handles primarily the layer below a hyper-converged or container-based solution. It often collaborates with the layers above through integrations such as the Kubernetes cluster autoscaler. [7]
BMaaS software has a similar objective to composable disaggregated infrastructure in that it aims to offer the user the ability to "compose" the desired compute unit defined as a set of resources (such as compute or storage). The distinction is that the storage and compute need not be "dissagregated" (accessed from outside the server unit) as this often requires specialized hardware. Instead, the same result is achieved with off-the-shelf hardware by selecting a matching server that matches the desired characteristics (RAM, CPU cores, local disk capacity, GPU, FPGA, SmartNICs) from a pool of servers and reconfiguring the network so that the server joins the others that a tenant has deployed.
Note that in some implementations, the storage component is external to the systems using iSCSI blurring the lines between BMaaS and composable infrastructure. This allows the user to choose the size and performance of the node's storage in a manner similar to classical virtualized Infrastructure as a Service offerings. This has the advantage of lower variability (snowflaking) in the hardware pool and the possibility of faster migration from one equipment to another in the event of hardware failure.
As new workloads such as augmented reality, mixed reality, connected cars, and telerobotics are gaining ground so is the demand for low latency cloud services so does demand for edge computing. [8]
Bare Metal and the BMaaS automation software is used for edge cloud implementations, where large numbers of small data-centers need to be automated and then consumed as a service and where the service needs to offer the lowest latency possible. [9]
At one time, all servers were bare-metal servers. Servers were kept on-premises and often belonged to the organisation using and operating them. Operating systems developed very early on (early 1960s) to allow time-sharing. Single large computers, mainframes or minis, were commonly housed in centralised locations and their services shared through a bureau. The shift to cheap commodity PCs in the 1980s changed this as the market expanded, and most organisations, even the smallest, began to purchase or lease their own computers. Popular growth of the internet, and particularly the web, in the 1990s encouraged the practice of hosting in data centres, where many customers shared the facilities of single servers. Small web servers at this time often cost more for their connectivity than their hardware cost, encouraging this centralisation. HTTP 1.1's ability for virtual hosting also made it easy to co-host many web sites on the same server.
From around 2000, or 2005 in commercially practical terms, interest grew in the use of virtual servers and then cloud hosting, where infrastructure as a service made the computing service the fungible commodity, rather than the server hardware. Hypervisors were developed which could offer many virtual machines hosted on larger physical servers. The load pattern of multiple users has long been recognised as being smoother overall than individual users, so these virtual machines could make more efficient use of the physical hardware and its costs, whilst also appearing to have higher individual performance than a simple cost-share would suggest.
One of the forefathers of bare metal provisioning is Cobbler that appeared in the 1990s and was using the Preboot Execution Environment (PXE) protocol. Since then various cloud providers have been building their own in-house stacks in order to offer variants of dedicated servers or bare metal cloud offerings such as:
for $335 million.
Examples of BMaaS software both open-source and commercial:
VMware LLC is an American cloud computing and virtualization technology company headquartered in Palo Alto, California. VMware was the first commercially successful company to virtualize the x86 architecture.
A virtual appliance is a pre-configured virtual machine image, ready to run on a hypervisor; virtual appliances are a subset of the broader class of software appliances. Installation of a software appliance on a virtual machine and packaging that into an image creates a virtual appliance. Like software appliances, virtual appliances are intended to eliminate the installation, configuration and maintenance costs associated with running complex stacks of software.
Desktop virtualization is a software technology that separates the desktop environment and associated application software from the physical client device that is used to access it.
VMware ESXi is an enterprise-class, type-1 hypervisor developed by VMware, a subsidiary of Broadcom, for deploying and serving virtual computers. As a type-1 hypervisor, ESXi is not a software application that is installed on an operating system (OS); instead, it includes and integrates vital OS components, such as a kernel.
Infrastructure as a service (IaaS) is a cloud computing service model by means of which computing resources are supplied by a cloud services provider. The IaaS vendor provides the storage, network, servers, and virtualization. This service enables users to free themselves from maintaining an on-premises data center. The IaaS provider is hosting these resources in either the public cloud, the private cloud, or the hybrid cloud.
Platform as a service (PaaS) or application platform as a service (aPaaS) or platform-based service is a category of cloud computing services that allows customers to provision, instantiate, run, and manage a modular bundle comprising a computing platform and one or more applications, without the complexity of building and maintaining the infrastructure typically associated with developing and launching the application(s), and to allow developers to create, develop, and package such software bundles.
oVirt is a free, open-source virtualization management platform. It was founded by Red Hat as a community project on which Red Hat Virtualization is based. It allows centralized management of virtual machines, compute, storage and networking resources, from an easy-to-use web-based front-end with platform independent access. KVM on x86-64, PowerPC64 and s390x architecture are the only hypervisors supported, but there is an ongoing effort to support ARM architecture in a future releases.
In computing, virtualization or virtualisation in British English is the act of creating a virtual version of something at the same abstraction level, including virtual computer hardware platforms, storage devices, and computer network resources.
The Rackspace Cloud is a set of cloud computing products and services billed on a utility computing basis from the US-based company Rackspace. Offerings include Cloud Storage, virtual private server, load balancers, databases, backup, and monitoring.
Cloud computing is the on-demand availability of computer system resources, especially data storage and computing power, without direct active management by the user. Large clouds often have functions distributed over multiple locations, each of which is a data center. Cloud computing relies on sharing of resources to achieve coherence and typically uses a pay-as-you-go model, which can help in reducing capital expenses but may also lead to unexpected operating expenses for users.
OpenStack is a free, open standard cloud computing platform. It is mostly deployed as infrastructure-as-a-service (IaaS) in both public and private clouds where virtual servers and other resources are made available to users. The software platform consists of interrelated components that control diverse, multi-vendor hardware pools of processing, storage, and networking resources throughout a data center. Users manage it either through a web-based dashboard, through command-line tools, or through RESTful web services.
OpenNebula is an open source cloud computing platform for managing heterogeneous data center, public cloud and edge computing infrastructure resources. OpenNebula manages on-premises and remote virtual infrastructure to build private, public, or hybrid implementations of Infrastructure as a Service and multi-tenant Kubernetes deployments. The two primary uses of the OpenNebula platform are data center virtualization and cloud deployments based on the KVM hypervisor, LXD/LXC system containers, and AWS Firecracker microVMs. The platform is also capable of offering the cloud infrastructure necessary to operate a cloud on top of existing VMware infrastructure. In early June 2020, OpenNebula announced the release of a new Enterprise Edition for corporate users, along with a Community Edition. OpenNebula CE is free and open-source software, released under the Apache License version 2. OpenNebula CE comes with free access to patch releases containing critical bug fixes but with no access to the regular EE maintenance releases. Upgrades to the latest minor/major version is only available for CE users with non-commercial deployments or with significant open source contributions to the OpenNebula Community. OpenNebula EE is distributed under a closed-source license and requires a commercial Subscription.
Wakame-vdc is an IaaS cloud computing framework, facilitating the provisioning and management of a heterogeneous virtualized infrastructure. Wakame-vdc virtualizes the entire data center; servers, storage, and networking. Wakame-vdc is managed via a native Web Interface, the Wakame-vdc CLI, or the powerful Wakame-vdc API.
CloudStack is open-source Infrastructure-as-a-Service cloud computing software for creating, managing, and deploying infrastructure cloud services. It uses existing hypervisor platforms for virtualization, such as KVM, VMware vSphere, including ESXi and vCenter, XenServer/XCP and XCP-ng. In addition to its own API, CloudStack also supports the Amazon Web Services (AWS) API and the Open Cloud Computing Interface from the Open Grid Forum.
openQRM is a free and open-source cloud-computing management platform for managing heterogeneous data centre infrastructures.
Software-defined storage (SDS) is a marketing term for computer data storage software for policy-based provisioning and management of data storage independent of the underlying hardware. Software-defined storage typically includes a form of storage virtualization to separate the storage hardware from the software that manages it. The software enabling a software-defined storage environment may also provide policy management for features such as data deduplication, replication, thin provisioning, snapshots and backup.
HP Cloud was a set of cloud computing services available from Hewlett-Packard. It was the combination of the previous HP Converged Cloud business unit and HP Cloud Services, an OpenStack-based public cloud. It was marketed to enterprise organizations to combine public cloud services with internal IT resources to create hybrid clouds, or a mix of private and public cloud environments, from around 2011 to 2016.
Oracle Cloud is a cloud computing service offered by Oracle Corporation providing servers, storage, network, applications and services through a global network of Oracle Corporation managed data centers. The company allows these services to be provisioned on demand over the Internet.
Citrix Virtual Desktops is a desktop virtualization product.
Harvester is a cloud native hyper-converged infrastructure (HCI) open source software. Harvester was announced in 2020 by SUSE.