VMware Software-Defined Storage. Martin Hosken
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for its integration into the market’s leading hypervisor, to ensure that software-defined storage can operate within a robust and affordable model. These initiatives, which are the focus of much of this book, include the following:
• The introduction of the hyper-converged infrastructure product Virtual SAN, a bare-bones, hardware-agnostic model with a direct-attached storage configuration. This reduces or removes altogether the requirement for a switched fabric or LAN-attached storage infrastructure to manage, with no more proprietary storage hardware to support.
• The abstraction of advanced storage functions away from the storage vendor, and instead placed in the hypervisor software and management control plane. This approach simplifies operations, with no more proprietary software licenses and firmware levels to manage, and enables storage services to be applied to all capacity, not just specific hardware.
• The introduction of a single storage service management plane, via a unified user interface. This removes the requirement for third-party tools and specific array element managers to monitor and administer a heterogeneous storage infrastructure.
All of these attributes provide a significant improvement over the ongoing challenges associated with classic storage infrastructures, although they do not address all the problems that make proprietary storage systems expensive to own and operate.
Hyper-Converged Infrastructure and Virtual SAN
The hyper-converged infrastructure (HCI) hardware architecture model uses the hypervisor to deliver compute, networking, and shared storage from a single x86 server platform. This software-driven architecture enables physical storage resources to become part of commodity x86 servers, enabling a building-block approach with a web-scale level of scalability. Also, by adopting this commodity x86 server hardware approach, and combining both storage and compute hardware into a single entity, IT organizations and cloud service provider data centers can operate with agility, on a highly scalable, cost-effective, fully converged platform.
Virtual SAN is VMware’s HCI platform, which enables this approach to be taken through the VMware integrated stack of technologies. Virtual SAN aggregates local storage into a unified data plane, which virtual machines can then use. Virtual SAN also uses a fully integrated policy-driven management layer, which allows virtual machines to be managed centrally, through a policy-driven storage mechanism that is integrated into the virtual machines’ own settings. These policies can define reliability, redundancy, and performance characteristics that must be obeyed, independently of all other virtual machines that may reside on the same storage platform.
Virtual SAN is the foundational component of VMware’s hyper-converged infrastructure solution. This model allows the convergence of compute, storage, and networking onto a single integrated layer of software that can run on any commodity x86 infrastructure aligned with the requirements set out on VMware’s hardware compatibility list (HCL). While vSphere abstracts and aggregates compute resources into logical pools, Virtual SAN, embedded into the hypervisor’s VMkernel, can pool together server-attached disk devices to create a high-performance distributed datastore.
This approach can easily meet the storage requirements of the most demanding IT organization or cloud service provider, at a lower cost than legacy monolithic SAN or NAS storage devices. Virtual SAN also allows vSphere and vSphere storage administrators to ignore concepts such as RAID sets and LUNs, and instead focus on the specific storage needs of applications. In addition, Virtual SAN can simplify capacity planning by scaling both storage and compute concurrently, allowing for the nondisruptive addition of new nodes, without the purchase of costly storage frames or disk shelves. Virtual SAN is addressed in more detail in Chapters 4–7.
Virtual Volumes
While they are not part of an HCI architecture strategy, Virtual Volumes is nevertheless an important component in VMware’s software-defined storage model. Virtual Volumes uses shared storage devices in a new way, and transforms storage management by enabling full virtual machine awareness from the storage array. Based on a T10 industry standard, Virtual Volumes provides a unique level of integration between vSphere and third-party vendors’ storage hardware, which significantly improves the efficiency and manageability of virtual workloads.
Virtual Volumes virtualizes shared SAN and NAS storage devices, which are then presented to vSphere hosts, providing logical pools of raw disk capacity, called a virtual datastore. Then, Virtual Volume objects, which represent virtual disks and other virtual machine entities, natively reside on the underlining storage, making the object, or virtual disk, the primary unit of data management at the array level, instead of a LUN. As a result, it becomes possible to execute storage operations with virtual-machine, or even virtual-disk, granularity on the underlining storage system, and therefore provide native array-based data services, such as snapshots or replication, to individual virtual machines.
To facilitate a simplified and unified approach to management, all this is done with a common storage-policy-driven mechanism, which encompasses both Virtual SAN storage resources and Virtual Volumes external storage, into a single management plane. Virtual Volumes is covered in more detail in Chapter 8, “Policy-Driven Storage Design with Virtual Volumes.”
Classic and Next-Generation Storage Models
This book refers to storage technologies as either classic or next-generation. Because these terms can have multiple meanings, this section provides an overview of each to clarify.
This book uses classic storage model to describe the traditional shared storage model used by vSphere. This typically includes LUNs, VMFS-based volumes and datastores, or NFS mount points, with a shared storage protocol providing I/O connectivity. Despite its constraints, this model has been successfully employed for years, and will continue to be used for some time by IT organizations and cloud service providers across the industry.
The next-generation storage model refers to VMware’s software-defined solutions, Virtual SAN and Virtual Volumes, which bring about a new era in storage design, implementation, and management.
As addressed earlier in this chapter, the primary aim of VMware’s software-defined storage model is to bring about simplicity, efficiency, and cost savings to storage resources. The model does this by abstracting the underlining storage in order to make the application the fundamental unit of management across a heterogeneous storage platform. With both Virtual SAN and Virtual Volumes, VMware moves away from the rigid constraints of the classic LUNs and volumes, and provides a new way to manage storage on a per virtual machine basis, through its more flexible policy-driven approach.
However, before addressing these next-generation storage technologies, you first need to understand the approach taken to storage over the last generation of vSphere-based virtualization platforms, and see how the VMware stack itself interacts with storage resources to provide a flexible, modern virtual data center.
This first chapter has addressed the VMware storage landscape, processes associated with storage design, and challenges faced by vSphere storage administration teams when maintaining complex, heterogeneous storage platforms on a daily basis for enterprise IT organizations and cloud service providers. The next chapter presents many of the essential design considerations based on the classic storage model previously outlined.
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Chapter 2
Classic Storage Models and Constructs
This chapter covers the design considerations for deploying classic storage technologies in a VMware-based virtual data center, and addresses the primary storage concepts that impact the platform design of the storage layer.
Classic Storage Concepts
Storage infrastructure is made up of a multitude of complex components and technologies, all of which need to interact seamlessly to provide high performance, continuous availability, and low latency across the environment. For students of vSphere storage, understanding the design and implementation complexities of mixed, multiplatform, multivendor