makers to grasp the concepts and challenges faced by the architect, and how they relate to their storage platform design.
When finances are stretched, as they so often are, a high storage infrastructure expenditure can significantly stand out on an IT executive’s annual budget spreadsheet. By examining the storage environment and calculating the total cost of ownership of storage resources, IT organizations can seek to identify new and innovative ways to address CapEx and OpEx expenditures through the software-defined storage model, without compromising application performance, capacity, availability or other data-related services.
Software-Defined Storage Summary
Just as VMware introduced x86 server virtualization to improve the cost metrics and utilization efficiencies of the compute platform, so too can the software-defined storage model be used to make the most efficient use of storage infrastructure, thereby reducing the total cost of ownership through storage acquisition and operational cost savings.
In the software-defined storage data center, all storage – whether it is directly attached hyper-converged Virtual SAN, or is SAN attached and leveraging Virtual Volumes–enabled arrays – can be used as part of a storage resource pool. This eliminates the requirement to rip and replace all of the storage infrastructure in order to adopt a fully hyper-converged unified storage model as part of a single migration project, and allows the IT organization to spread the costs associated with a full storage infrastructure refresh over a number of years.
This is only one storage strategy. Equally valid is the mixed hybrid approach of employing Virtual Volumes and Virtual SAN as a long-term design, effectively using both solutions for specific use cases and workloads, as illustrated in Figure 1.10.
Figure 1.10 Hybrid Virtual Volumes and Virtual SAN platform
Just like the classic storage model, large enterprise customers and cloud service providers that are adopting software-defined storage typically should configure resources into pools. Each pool is composed of a different set of characteristics and services.
For instance, a Virtual SAN tier 1 pool may be optimized for performance and business-critical workloads, while a tier 0 pool may comprise all-flash disk groups and provide storage resources to specific I/O-intensive workloads. Following a similar model, high-capacity, low-cost, low-performance disks may be fashioned into a pool intended for the data that is infrequently accessed or updated. With this type of approach to storage provisioning, the software-defined storage model will continue to enable the implementation of a tiered storage strategy in order to provide improved capacity utilization and resource efficiency.
Furthermore, the implementation of a software-defined storage model allows technologies such as thin provisioning, compression, and de-duplication to be applied across an entire storage platform, rather than isolating these features behind specific hardware controllers. This helps to ensure that storage capacity can be used more efficiently, via a global storage policy.
These technologies can help slow the rate at which new capacity must be added to the infrastructure, and help ensure that where appropriate, less-expensive hardware can be deployed. In addition, centralizing this functionality through a single control plane enhances ease of administration, which in turn can also help reduce operational costs and the efforts associated with software maintenance.
The software-defined storage model is not an industry standard, and various approaches exist for the design, implementation, and function of the solution stack. Both VMware and independent software vendors (ISVs) have in recent years developed the concepts and product architecture of the software-defined storage platform 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
