VMware vSAN stands as a cornerstone of the modern Software-Defined Data Center (SDDC), offering robust, high-performance, and scalable storage solutions integrated directly into the hypervisor. As the technology evolves, keeping up with the latest advancements is crucial for architects, administrators, and IT professionals. This article distills the essential takeaways from the comprehensive VMware vSAN FAQ document, providing a clear overview of its core concepts, latest features, and deployment architectures. For a more interactive deep dive, be sure to check out my upcoming video walkthrough on this topic, created with NotebookLM.
Core Architectural Pillars: OSA vs. ESA
vSAN offers two distinct architectures: the Original Storage Architecture (OSA) and the newer, high-performance Express Storage Architecture (ESA). Understanding their differences is key to designing and deploying a modern vSAN cluster.
|
Feature |
Original Storage Architecture (OSA) |
Express Storage Architecture (ESA) |
|
Storage Devices |
Supports SAS, SATA, and NVMe devices. |
Exclusively uses NVMe-based devices. |
|
Tiering |
Uses a two-tier model with a cache tier (for writes) and a capacity tier. |
Employs a single-tier design where all devices contribute to both cache and capacity. |
|
Data Structure |
Organizes devices into "disk groups," each with one cache and up to seven capacity devices. |
Uses a "storage pool" of devices per host, eliminating the disk group construct. |
|
Performance |
Performance is often gated by the cache tier and disk group limitations. |
Delivers near device-level performance by removing bottlenecks and optimizing the data path. |
|
Space Efficiency |
Deduplication and compression are performed at the cluster level, which can impact performance. |
Offers highly efficient, policy-based compression and global deduplication with minimal performance overhead. |
|
RAID-5/6 |
Requires a minimum of 4 hosts for RAID-5. |
Supports efficient RAID-5 on as few as 3 hosts, delivering RAID-1-like performance. |
While the OSA remains a viable option for existing hardware, all new deployments should be designed for the ESA to leverage its superior performance, efficiency, and lower Total Cost of Ownership (TCO) .
Flexible Deployment Models
vSAN is not a one-size-fits-all solution. It provides several deployment models to cater to different infrastructure needs, from the data center core to the edge.
•vSAN HCI (Hyperconverged Infrastructure): This is the traditional, aggregated model where compute and storage resources reside within the same cluster. It simplifies management and is ideal for a wide range of workloads.
•vSAN Storage Clusters: Previously known as vSAN Max, this disaggregated model separates compute and storage into independent clusters. It allows you to scale storage and compute resources independently, providing a centralized, highly scalable storage platform for multiple vSphere clusters. This is particularly beneficial for optimizing licensing costs and managing large-scale environments .
•Stretched and 2-Node Clusters: These topologies provide high availability and site-level resilience. Stretched clusters span two geographic locations, while 2-Node clusters are designed for Remote Office/Branch Office (ROBO) and edge environments, using a third-site witness to maintain data quorum.
Key vSAN Capabilities
Beyond its architecture, vSAN is packed with features that ensure data availability, security, and operational simplicity.
Availability: vSAN protects against failures at multiple levels, including individual disks, entire hosts, and even network partitions. By setting Storage Policy-Based Management (SPBM) rules like "Failures to Tolerate" (FTT), administrators can define the desired level of data redundancy for each virtual machine.
Security: vSAN provides both Data-at-Rest and Data-in-Transit encryption using the AES-256 cipher. This can be managed through external Key Management Service (KMS) solutions or the vSphere Native Key Provider (NKP), without requiring specialized self-encrypting drives (SEDs) .
Performance and Operations: Tools like HCIBench allow for standardized performance testing, while features like adaptive resynchronization minimize the performance impact of maintenance operations. The Skyline Health service in vCenter provides comprehensive monitoring and proactive diagnostics to ensure your cluster runs optimally.
Explore Further
The world of vSAN is deep and constantly evolving. This article provides a high-level overview of the key concepts you need to know. To get the full details and answers to more specific questions, I highly recommend exploring the official documentation.
As you continue your learning journey, be sure to watch my upcoming video where I walk through these concepts in more detail using NotebookLM.
References
[1] VMware. (2025, December 12). vSAN Frequently Asked Questions.
