Software-Defined Data Center
The term SDDC, short for Software-Defined Data Center, is commonly used in the IT industry, especially in virtualization technology. SDDCs essentially virtualize the entire data center infrastructure, including compute, storage, and network components. This virtualization allows for the abstraction of physical hardware into virtual pools, enabling more efficient resource utilization.
Since the components of the data center are software-based, the configuration is more agile, and provisioning parts and services can be done much faster compared to traditional physical data centers.
Clouds
SDDCs are often part of a cloud environment, which can consist of one or multiple SDDCs. A private cloud refers to an SDDC infrastructure hosted on-premise or on-site, while a public cloud is an SDDC infrastructure hosted off-premise or off-site, often in a rented data center facility or through a hosted Infrastructure as a Service (IaaS) offering.
Compute Virtualization
Compute virtualization abstracts the hardware layer, allowing multiple virtual components to share the same hardware. This means that the CPU and RAM can be shared among multiple virtual machines, each running its own operating system.
Before Virtualization
Before the advent of virtualization, physical hardware could only host one operating system at a time. While multiple applications could run on top of this OS instance, the utilization of physical hardware was inefficient.
Use Cases for Virtualization
Virtualizing physical compute resources has several key benefits, including:
Efficient Use of Resources
Virtualization allows for the abstraction of physical hardware, enabling multiple virtual servers to run on the same hardware. This allows for resource sharing and more efficient resource utilization.
Security
Virtualization also provides security benefits by enabling the segregation of applications. For instance, if you have a critical application that requires a secure, isolated environment, you can run it within its own virtual server (virtual machine) to ensure that no other applications can negatively impact it.
Automation
Utilizing a virtualized server infrastructure constructed primarily with software offers the advantage of saving time and ultimately reducing costs by automating entire application tiers comprising multiple virtual machines.
After Virtualization
Following virtualization, virtual machines share the same physical hardware, as depicted in Image 3.1. Each virtual machine can operate its operating system, isolated from other operating systems running on different virtual machines.
The hypervisor acts as the (software) intermediary between the physical and virtual components. It mimics or emulates the available physical resources and translates them into virtual components that virtual machines can utilize.
Image 3.1 illustrates an example of a type-1 hypervisor. In this type, the hypervisor serves as the operating system, distinct from the operating system used for a virtual machine. This type of hypervisor is renowned for its performance, as there is no additional overhead of another operating system consuming additional resources.
Examples of type-1 hypervisors in the current market include VMware ESXi, Oracle VM, Microsoft Hyper-V, KVM (Kernel-Based Virtual Machine), and Citrix Hypervisor (formerly Xen Server). A type-2 hypervisor, also known as a "hosted hypervisor," requires an operating system to function. This operating system could be Apple's macOS, Microsoft Windows, or a Linux distribution. The type-2 hypervisor then operates on top of this operating system, as shown in Image 3.2.
Containers
A container is a further level of virtualization where virtualization occurs at the operating system level, as depicted in Image 4.1
Containers allow you to develop and run applications inside a container, which can be swiftly and efficiently moved when necessary, enhancing scalability. If the operating system is slow or unavailable, a new container can be brought up, and your application and code can be operational again in seconds. The container engine manages container management.
The general principle is that virtual machines isolate operating systems using hypervisors, while containers isolate applications using container engines on top of an operating system.
Combining virtual machines and containers is also possible, as shown in Image 4.2. Here, the container engine runs on top of the hypervisor and manages containers hosted inside different virtual machines.
Storage Virtualization (Software Defined Storage | SDS)
Software-defined storage allows the pooling of various physical storage devices from multiple sources to present them as a single volume to the operating system and/or application.
Network Virtualization (Software Defined Networking | SDN)
Software-defined networking (SDN), also known as network virtualization (NV), abstracts physical network resources to deliver network resources and services in a virtualized manner. Decoupling network services from the underlying physical network enables a new level of scalability and flexibility.
Network services such as routing, switching, VPN, and load balancing can now be provided on the software layer instead of the physical layer. This enables programmatically configuring most of these services, reducing administrative overhead and facilitating faster provisioning with fewer errors compared to manual provisioning of network services.
VMware SDDC
VMware's implementation of the software-defined data center.
VMware vSphere
VMware vSphere comprises two (software) products that enable the virtualization of the computing layer: VMware ESXi Server and VMware vCenter Server.
VMware ESXi Server (Hypervisor)
VMware ESXi Server serves as VMware's compute (type-1) hypervisor. Installed on a physical server, ESXi Server acts as both the operating system and hypervisor (Image 5.1).
VMware vCenter Server
vCenter Server serves as the management environment/component of VMware vSphere. It allows for the administration of all ESXi servers in an environment from a single interface, providing centralized management of the entire vSphere environment (Image 6.1). vCenter Server also facilitates the configuration of virtualization-related features related to computing and storage virtualization (VSAN).
VMware Virtual Storage Area Network (VSAN)
VSAN represents VMware's implementation of software-defined storage (SDS). Integrated with vSphere, VSAN presents itself as a single data store from a virtual perspective. The storage is constructed using multiple ESXi hosts with multiple physical disks, which are pooled together to present a unified data store to the vSphere infrastructure (Image 7.1).
NSX-v and NSX-T
NSX serves as VMware's implementation of software-defined networking (SDN) (Image 8.1). Currently available in two versions—NSX-v (NSX for vSphere) and NSX-T—NSX offers various network services such as routing, switching, load balancing, VPN, firewalling, and bridging as its primary services. NSX also includes additional network services, which are further discussed in subsequent chapters.
Note: NSX-v has been announced as the end of sale/end of support, with NSX-T being its successor and the recommended NSX software for future deployments.
VMware VCF
VMware Cloud Foundation (VCF) offers VMware's complete SDDC software in a bundle that ensures software versions and interoperability are thoroughly validated for full compatibility. VCF includes vSphere, VSAN, and NSX as its core components (Image 8.1). Additionally, VCF includes other VMware software packages, though these are beyond the scope of this book.
Summary
This chapter has elucidated the software-defined data center (SDDC) and its various virtualized components. It has explained compute, storage, and network virtualization, as well as the distinction between a virtual machine and a container. Finally, it has outlined VMware's specific implementation of the SDDC, detailing the VMware products that constitute the SDDC. The next chapter will introduce NSX-T.
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