VMware vSAN Requirements and Best Practices: A Comprehensive Guide

by Davoud Teimouri · Published 30/01/2025 · Updated 30/01/2025

VMware vSAN is a powerful, software-defined storage solution that makes storage management easier by pooling local disks from ESXi hosts into a single storage platform. Its close integration with vSphere makes it a popular choice for organisations looking to modernise their infrastructure. However, implementing vSAN effectively necessitates a thorough understanding of its requirements and best practices.

This guide discusses VMware vSAN’s requirements, fault domain configurations, disk group design, host recommendations, and comparisons to block storage solutions such as Dell PowerStore and Unity. It also covers database deployment on vSAN and offers actionable tips to ensure a successful implementation.

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VMware vSAN Requirements and Best Practices

VMware vSAN has basic requirements for creating cluster but the requirements are enough when you are creating cluster for very small business and the business has no concern about data availability and service availability. Let’s review the requirements and best practices that covers range of small to enterprise businesses.

Number of Hosts in a Cluster

The number of hosts in a VMware vSAN cluster directly impacts scalability, performance, and fault tolerance.

Minimum Requirements

A 2-host vSAN cluster is the smallest configuration, supported by an external witness appliance for quorum. This setup is cost-effective but lacks advanced features and scalability.
A 3-host cluster removes the need for a witness node and provides basic redundancy using RAID 1.

Recommended Configuration

VMware recommends a minimum of 4 hosts for production environments. A 4-host cluster enables RAID 5 and RAID 6 configurations, allowing for dual-failure tolerance while supporting maintenance operations without compromising availability.

Best Practices:

Use a minimum of 4 hosts for production to ensure fault tolerance and resilience.
For mission-critical workloads, add more hosts to accommodate growth and provide additional failover capacity.

Number of Hosts	Supported Features	Fault Tolerance	RAID Levels	Use Case
2	Basic with witness node	Single failure	RAID 1	Edge or small branch offices
3	Full vSAN functionality	Single failure	RAID 1	Small-scale production environments
4+	Advanced RAID 5/6	Dual failure	RAID 1, 5, 6	Medium to large production environments

Fault Domains

Fault domains are essential for achieving higher resilience in vSAN by distributing data intelligently across hosts to withstand failures affecting multiple components (e.g., racks or power supplies).

What Are Fault Domains?

A fault domain is a logical grouping of hosts in a vSAN cluster. By default, vSAN treats each host as an independent fault domain. However, for larger deployments, administrators can manually configure fault domains to protect against rack or power-related failures.

Why Fault Domains Matter

In large clusters, the failure of an entire rack (or a group of hosts) can lead to data loss if fault domains are not configured. For example:

Without fault domains, vSAN may store all replicas of an object on hosts in the same rack, risking data availability if the rack fails.
With fault domains, vSAN ensures that replicas are distributed across racks, significantly enhancing data protection.

Best Practices for Fault Domains

Align Fault Domains with Physical Infrastructure: Create fault domains based on racks, power sources, or network segmentation.
Minimum Requirement: At least 3 fault domains are required for fault domain redundancy.
Cluster Size Considerations:
- For 6-8 hosts: Configure at least 3 fault domains.
- For clusters with 9 or more hosts: Use 4 or more fault domains for optimal protection.
Testing and Validation: Regularly test the fault domain configuration to ensure compliance with vSAN policies.

Cluster Size	Fault Domains Required	Purpose
3-5 Hosts	Fault domains optional	Focus on expanding hosts before domains
6-8 Hosts	Minimum 3 fault domains	Resilience against rack or power failures
9+ Hosts	4 or more fault domains	Enhanced protection and scalability

Disk Group Design and Best Practices

Disk groups are the building blocks of VMware vSAN storage. They consist of:

Caching Tier: Accelerates I/O operations.
Capacity Tier: Stores persistent data.

Caching Tier

The caching tier improves read and write performance. NVMe or SSD drives are recommended for caching, especially in all-flash configurations.

Best Practice:

Allocate 10% of the total capacity tier size to the caching tier.
Use enterprise-grade NVMe drives for high-performance workloads.

Capacity Tier

The capacity tier contains the majority of the data and is critical for scalability. All-flash configurations offer superior performance, while hybrid configurations are cost-effective for less demanding workloads.

Best Practice:

Use all-flash configurations for latency-sensitive applications.
Enable deduplication and compression to optimize storage space.

Multiple Disk Groups

Adding multiple disk groups per host enhances redundancy and performance.

Best Practice:

Configure at least two disk groups per host.
Distribute workloads evenly across disk groups to avoid bottlenecks.

Configuration	Benefits	Limitations
Single Disk Group	Simplifies setup for small environments	Limited fault tolerance and performance
Multiple Disk Groups	Improves performance and redundancy	Requires more hardware resources

VMware vSAN vs. Block Storage

Block storage solutions like Dell PowerStore and Unity remain popular for traditional IT workloads. Here’s how they compare to vSAN:

Feature Comparison

Feature	vSAN	Block Storage (PowerStore/Unity)
Architecture	Software-defined, hyper-converged	Hardware-based, appliance model
High Availability	Built-in RAID 5/6	Advanced HA with array replication
Cost	Lower for VMware environments	Higher upfront costs
Scalability	Horizontal (add hosts)	Vertical (add storage arrays or capacity)
Workload Focus	Virtualized environments	Physical and virtualized workloads
Performance	Optimized for VMs	Superior for high-performance databases

Strengths and Weaknesses

vSAN Strengths

Deep integration with vSphere simplifies deployment and management.
Flexibility to scale with hosts rather than dedicated storage arrays.
Cost-efficient for organizations already using VMware.

vSAN Weaknesses

Dependent on host resources, which can limit scalability.
Performance may degrade with improper configuration.

Block Storage Strengths

Superior performance for high IOPS workloads like transactional databases.
Established features like snapshots and replication.

Block Storage Weaknesses

Less flexibility compared to hyper-converged solutions.
Higher cost and complexity for initial deployment.

Database Implementation on VMware vSAN

Workload Characteristics

Databases generate complex I/O patterns, requiring low latency and high throughput. vSAN meets these demands through caching and RAID configurations.

Storage Policies

vSAN storage policies allow precise control over database performance and availability.

Best Practices:

Configure an FTT of 2 for critical databases.
Use RAID 5 or RAID 6 for cost-efficient data protection.

Monitoring and Optimization

Regular monitoring ensures databases perform optimally. Use vRealize Operations for tracking metrics like IOPS and latency.

Conclusion: The Key to a Successful VMware vSAN Deployment

VMware vSAN revolutionizes storage for virtualized environments by delivering scalability, resilience, and simplicity. However, its success depends on proper planning, especially regarding hosts, fault domains, and disk groups.

Key Takeaways

Host Configuration: Start with a 4-host cluster to enable advanced features like RAID 5/6.
Fault Domains: Essential for protecting against larger failures. Configure fault domains for clusters with 6+ hosts.
Disk Groups: Optimize caching and capacity tiers to align with workload requirements.

When compared to block storage, VMware vSAN shines for virtualized environments, while traditional block storage remains the preferred choice for physical workloads and high-performance databases. By carefully evaluating requirements and adhering to best practices, organizations can leverage vSAN to meet the demands of modern applications and future-proof their infrastructure.