vSAN Original Storage Architecture (OSA) & Express Storage Architecture (ESA) 

3 mins. read
Keerthikumar K R
Senior Consultant Hybrid Cloud

VMware vSAN is a software-defined enterprise storage solution that supports hyper-converged infrastructure (HCI) system. vSAN is fully integrated with VMware vSphere, as a distributed layer of software within the ESXi hypervisor. It enables a single data-store in the vSphere cluster to facilitate the storage service for the workloads.  

Why vSAN?

VMware vSAN continues to be the Hyperconverged Infrastructure (HCI) market leader. vSAN has proven to be an excellent fit for all types of workloads. Traditional applications like Microsoft SQL Server and SAP HANA; next-generation applications like Cassandra, Splunk, and MongoDB; and even container-based services orchestrated through Kubernetes are run on vSAN by customers today. The success of vSAN can be attributed to many factors such as performance, flexibility, ease of use, robustness, and pace of innovation.

VMware vSAN is helping customers move forward with their digital transformation. Today, over 30,000 customers have trusted HCI-powered VMware vSAN in their data centers. There are three main benefits of adopting vSAN:

  1. Lower Total Cost of Ownership (TCO)

The traditional data center is built with traditional storage, making it capital-intensive and costly to maintain. To help reduce the costs, customers are turning to HCI powered by vSAN to get the most benefit out of their purchases. Customers can enable vSAN’s ability on standard x86 servers to lower storage costs. In addition to dropping lower upfront costs, it reduces operational costs by shrinking the data center footprint, power usage and cooling costs, equating to significant cost savings, particularly in a time of rising energy prices.

Some customers feedback on adopting vSAN as principal storage.

Note: above customer’s feedback examples are taken from VMware site.

  1. Accelerate Operations

Another challenge enterprises face with traditional storage is the separate management of each infrastructure component. Each separate management system is managed by a dedicated specialist. IT admins can spend weeks provisioning the infrastructure to support new applications, making it cumbersome and less efficient.

VMware HCI powered by vSAN architecture allows a single team of IT admins to manage their compute and storage environment from tools they already know, vCenter and the vSphere client. IT administrators experience a faster learning curve adopting vSAN because they use a familiar and extensible management solution. According to a Compass Partner study, VMware HCI reduces time spent on routine tasks by more than 50% with simplified processes performed by a unified infrastructure team. With administrators reducing time spent on manual, repeatable tasks, they can focus on value-added tasks that move the business forward. The key to vSAN’s ability to reduce time on tasks is storage policy-based management, or SPBM. SPBM allows IT admins to set policies for application requirements for capability, performance, availability and more in vCenter. This automation increases business agility and reduces manual interventions for common tasks, monitoring and troubleshooting.

Some customers feedback on managing vSAN storage.

Note: above customer’s feedback examples are taken from VMware website. 

  1. Developer and Multi-Cloud Ready

VMware HCI powered by vSAN enables a future-proof IT environment, with support for today’s traditional applications and new cloud-native applications and platform such as Tanzu & Kubernetes. VMware HCI powered by vSAN integrates with VMware Tanzu to provide a single storage platform for virtual machines (VMs) and containers. It provides developers with the self-service capabilities to create apps at scale while providing IT administrators the governance and insights to manage the infrastructure.

On the hybrid, VMware vSAN’s flexible architecture allows IT to extend it to cloud providers to a multi-cloud operating model. VMware vSAN is a key component of VMware Cloud Foundation hybrid cloud platform. 

The platform can extend to the public cloud like Amazon with VMware Cloud on AWS and other top cloud providers- Microsoft, Google, IBM, Oracle and over 500 public cloud providers, further simplifying cross-cloud workload migration. This flexibility is key for IT and development teams to move swiftly and efficiently to innovate faster than the competition.

Use cases of vSAN

  • Multitenancy in vSAN

Service providers or any organization that provides resources to more than one customer or tenant have a unique subset of needs that extend beyond the typical concerns of data center design and operations.  Is a tenant's data isolated to meet their security and prioritization criteria?  And what does "isolated" even mean in the world of shared resources?  Can resources be managed and prioritized in a manner that reflects the different needs of these customers?  These are non-trivial matters that often do not have a simple yes or no answer, but rather, a degree of acceptability that depends on requirements.

The value gained by sharing resources may conflict with three topics that are important to service providers, and their tenants viz., Management of resources, Security of resources and Prioritization of resources.  

vSAN will facilitate and address all the above concerns for Multitenancy.  

  • vSAN Remote Office Deployment

VMware vSAN is the industry-leading software powering Hyper Converged Infrastructure (HCI) solutions. vSAN is optimized for VMware vSphere virtual machines and natively integrated with vSphere. Since drives internal to the vSphere hosts are used to create a vSAN datastore, there is no dependency on expensive, difficult to manage, external shared storage.

Remote office environments can benefit from shared storage while reducing total cost of ownership. Deploy vSAN on two or more physical vSphere hosts using industry-standard server components to avoid large, up-front investments in purpose-built storage hardware. Lower operational expenses by automating management of storage services through policies. 

  • VMware vSAN for Disaster Recovery

Lowering the Risk and Cost of DR VMware vSAN provides a cost-effective storage solution that is fast, reliable, and resilient to run business critical workloads in the event of a disaster recovery.

vSAN architecture 

vSAN is VMware’s software-defined storage solution, built from the ground up for vSphere virtual machines.

It abstracts and aggregates locally attached disks in a vSphere cluster to create a storage solution that can be provisioned and managed from vCenter and the vSphere Client. vSAN is embedded within the hypervisor, hence storage and compute for VMs are delivered from the same x86 server platform running the hypervisor.

                                                           Figure 1: vSAN Architecture

vSAN can be implemented in two architectures (explained below) that is subjected to the hardware and networking requirements. 

  • vSAN Original Storage Architecture (OSA)
  • vSAN Express Storage Architecture (ESA) 

  1. vSAN Original Storage Architecture (OSA)

In vSAN Original Storage Architecture consists of two tiers: a cache tier for the purpose of read caching and write buffering, and a capacity tier for persistent storage. This two-tier design offers supreme performance to VMs while ensuring that devices can have data written to them in the most efficient way possible. vSAN uses a logical construct called disk groups to manage the relationship between capacity devices and their cache tier.


  1. Express Storage Architecture (ESA) 

VMware believes the vSAN Express Storage Architecture is ideal for all of our customers and cloud providers moving to this latest generation of hardware.  Delivering space-efficient and highly resilient storage without any performance compromise, using all claimed storage devices for capacity, and new compression enhancements significantly change the mathematics in favor of the vSAN ESA. 

vSAN had already solved many of the great challenges associated with distributed storage systems, and VMware wanted to build off of these capabilities while looking at how best to optimize a data path to reflect the capabilities of today's hardware.

The advances in architecture primarily come from two areas, 

A new patented log-structured file system (LFS).

This new layer in the vSAN stack - known as the vSAN LFS - allows vSAN to ingest new data fast and efficiently while preparing the data for a very efficient full stripe write.  The vSAN LFS also allows vSAN to store metadata in a highly efficient and scalable manner.

DiagramDescription automatically generated

Figure 2 Integrating an optional, hardware-optimized architecture into vSAN.

DiagramDescription automatically generated

Figure 3: Data processing in lower layers in vSAN OSA

An optimized log-structured object manager and data structure.  

This layer is a new design built around a new high-performance block engine and key value store that can deliver large write payloads while minimizing the overhead needed for metadata.  The new design was built specifically for the capabilities of the highly efficient upper layers of vSAN to send data to the devices without contention.  It is highly parallel and helps us drive near device-level performance capabilities in the ESA.

Figure 4: Optimized data handling in the vSAN ESA

New Capabilities and Better Results

  • The space efficiency of RAID-5/6 erasure coding with the performance of RAID-1 mirroring.
  • Adaptive RAID-5 erasure coding for guaranteed space savings on clusters with as few as 3 hosts.
  • Storage policy-based data compression offers up to 4x better compression ratios per 4KB data block than the vSAN OSA.
  • Encryption that secures data in-flight and at rest with minimal overhead.
  • Adaptive network traffic shaping to ensure VM performance is maintained during resynchronizations.
  • The lower total cost of ownership (TCO) by removing dedicated cache devices with the flexible architecture using a single tier in vSAN 8.
  • Simplified management, and smaller failure domains by removing the construct of disk groups.
  • New native scalable snapshots deliver extremely fast and consistent performance.  Achieve backups more quickly through snapshot consolidations that are up to 100x faster.

vSAN Licensing

VMware vSAN can be licensed on a per Core metric and is offered across Standard, Advanced, Enterprise, and vSAN+ editions in 1-, 3-, and 5- year subscription terms. There is a minimum licensing requirement of 16 cores per CPU.  

There are two types of subscription licenses available: cloud connected subscriptions and disconnected term subscriptions. 

The differences between the two are that cloud connected subscriptions, such as vSAN+, require a cloud connection and utilize a keyless licensing mechanism to provide entitlement to the customer for the subscription. 

The disconnected term subscriptions do not require a cloud connection and utilize license keys to provide entitlement to the customer for the subscription. 

vSAN Perpetual Licensing VMware vSAN can be licensed on per CPU, per concurrent user in 10 or 100 license packs for virtual desktop infrastructure (VDI), and per virtual machine (VM) in 25-VM license packs for remote office/branch office (ROBO) implementations. 

vSAN Standard, Advanced, and Enterprise editions can be licensed on these three metrics except for vSAN Enterprise Plus, which is only available on a per-CPU license. 

Note, a support and subscription (SnS) contract is required for perpetual licenses. For any software offering that VMware licenses on a per-CPU basis, VMware requires one license for up to 32 physical cores. If a CPU has more than 32 cores, additional CPU licenses will be required. 

Packaging overview vSAN+ is the premier HCI offering which delivers cloud-connected services for IT admins to centralize management and enhance efficiency.  vSAN term license editions include Standard, Advanced, and Enterprise.  vSAN perpetual license editions include Standard, Advanced, Enterprise and Enterprise Plus.  Table 1 shows the product features included in each offering.

Note: licensing information is taken from VMware website. 

How Huco Helps Our Customers in adopting HCI vSAN?

VMware HCI powered by vSAN is key to a company’s digital transformation and application modernization journey. Its flexible architecture simplifies the complexity of IT environments so our customers can innovate faster, save money, and simplify private cloud enablement. Our customers are seeing huge dividends arising out of VMware HCI implementations powered by vSAN. 

Are you ready to start your journey with VMware vSAN?

We collaborate with customers to design, consult, and implement VMware vSAN to derive business and technology benefits HCI driven software defined storage.

For more information on how Huco helps customers in transforming and adopting VMware vSAN, please reach out to info@huco.co  and post your inquiry/interest. Our VMware Experts are eager to help you in your journey towards VMware HCI powered by vSAN.

Get in touch with us
Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.