Traditionally, storage was confined to the server's hardware; eventually, due to the increasing demand for storage capacity, availability, and centralized management, there was a need for a robust system to manage storage provisioning and maintenance. This lead to the evolution of storage area network (SAN) and Network Attached Storage (NAS). While a typical Fiber Channel, SAN, proved to be quite expensive, particularly the Fabric switch and the array itself, it also had other form factors that leveraged the existing network infrastructure in the form of iSCSI and NFS. Interestingly, a complete cycle of evolution is taking place and we are heading back toward storage being confined to the server and forming one of the methodologies of achieving Software-Defined Storage.

In a typical data center, we have several types of resource-intensive workloads that can be compute-, network-, memory-, or disk- intensive. While the compute and network needs are serviced by server virtualization solutions, such as ESXi, and network virtualization solutions, such as NSX, all the workloads need disk capacity, but with varying requirements in terms of redundancy and performance. The storage resources need to be elastic and dynamic, catering to different I/O requirements.

This implied that we needed a much more granular and dynamic management of the storage infrastructure, and such a degree of control can only be achieved at the software stack; we needed Software-Defined Storage.

Very simply put, Software-Defined Storage can be defined as a storage infrastructure that can be fully managed at the software stack.

Software-Defined Storage is truly aligned with the SDDC vision of the abstraction, pooling and automation of all the data center's resources.

The deliverable of Software-Defined Storage is a Virtual Data Service that is policy - driven; the three primary attributes of this deliverable are:

While the SDS market is densely populated with various different players, the market is highly disruptive and evolving heavily, we will look at a few form factors available as on date.

To better understand the value proposition of SDS, one should understand the current state of affairs, options at disposable, and the advantages of each option leading to the newest fad in enterprise storage; in this section, we will closely evaluate these options.

Hyper-converged solutions

As the name indicates, Hyper-converged solutions unify the compute, storage and/or network under one roof. That is, one or more vendors will provide a packaged solution that will come in the form of a set of hardware that provides storage and network capabilities with a choice of hypervisors such as VMware ESXi or Microsoft Hyper-V.

In summary, Hyper-converged solutions arguably pose as hybrid solutions stemming out off and, effectively, may replace traditional SAN and Software-based Storage.

Of particular importance in this area and a key differentiator among the rest, is the VMware VSAN solution, wherein an abstraction layer for storage is in-built in the hypervisor. VMware has cranked up a notch ahead on this note and carved out a significant milestone with EVO: RAIL, an evolutionary Hyper-Converged Infrastructure Appliance (HCIA). This is done in partnership with an elite list of hardware vendors, in essence, vSphere and Virtual SAN are sold and supported in a box.

So what's the big difference?

• VSAN natively understands vSphere Storage needs—this is crucial in terms of performance
• Other Hyper-converged vendors need a controller VM to provide the storage abstraction, while for VSAN, this becomes a feature to be enabled
• With some basic configuration settings after racking and stacking, you are ready to deploy the VMs
• There is a single point of support for all issues
• There is no specialized skill set needed to be a vSphere administrator than a bit of reading from this book!!!
• In particular, EVO: RAIL is an all-inclusive licensing model, shipping with vSphere Enterprise Plus 5.5 U2 and includes the licenses needed for vCenter, ESX, VMware VSAN, and LogInsight

EVO: RAIL carves out an SDDC with these simple steps:

1. Procuring the appliance, racking and stacking it
2. Connecting to the top of the rack switch
3. Attaching your laptop to the switch and connecting to the RAIL IP address

If you are in a real hurry, just click on "Just Go!" and you are all set to deploy Virtual Machines.

Here is a sneak peek at the configuration screen of EVO: RAIL:

Here is the definition provided by VMware—"VMware Virtual SAN is a new software-defined storage tier for VMware vSphere environments. Virtual SAN clusters server disks and flash to create radically simple, high - performance, resilient shared storage designed for virtual machines."

They say history repeats itself; true to this, we have completed a cycle moving from server-based in-built storage to storage array networks (SAN), we did this primarily for the following two basic key requirements:

Hence, moving to SAN storage addressed these requirements and brought to the table many more advantages, it also brought a challenge along in terms of cost.

The cost factor was, by itself, a significant driver to move away from the SAN infrastructure back into server-based storage.

VMware Virtual SAN is one such solution (arguably the best) that eliminates the limitations of server-based storage and optimizes performance by coupling hard disks with flash storage in its first generation. With the latest release, VSAN 6.0 supports all flash storage.

At a high level, the following diagram depicts a four node cluster that provides HDDs and SSDs formulating a Virtual SAN Clustered Datastore which, in turn, serves as the abstraction layer on which vSphere platform provides the disk capabilities for the Virtual Machine deployment.

Furthermore, we can implement granular control to frame individual virtual machine-level policies. Through policies, we can govern service-level agreements and the requirements of the workloads.

At the very root, while designing a virtual machine, the requirements are driven by the operating system and the application that will be contained in the virtual machine, that is, the requirements in terms of CPU, memory, disk, and network. All of the resources need to work in tandem to ensure that the end user experience meets the expectations/service-level agreements. From a disk perspective, the business will be interested in IOPS and redundancy, these requirements are embedded in virtual machine storage policies that will ensure that a virtual machine obtains the entitled resources during its lifecycle.

The future of IT is inclined toward a Software-defined Datacenter, whether it is on-premises or off-premises. Software-defined storage is the factor that accelerates this adaption by providing a very high degree of control and dynamism to Storage Management and Provisioning. While the directive is clear, the means of achieving software-define storage are aplenty. The question is, which solution will be optimal and be more advantageous than the rest? There are very strong indicators that a hybrid model that is cost-effective will lead the way, VMware have their noses ahead with Virtual SAN & EVO: RAIL. We have discussed the options available thus far and will closely assess the nitty-gritty aspects of VMware Virtual SAN in the upcoming chapters.