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Wednesday, June 12, 2024

Optimizing Your Virtual World: Selecting the Right Fit - vSAN ESA or vSAN OSA for VCF 5.1.x

Optimizing Your Virtual World: Selecting the Right Fit - vSAN ESA vs. vSAN OSA for VCF 5.1.x

Are you considering deploying VCF 5.1.x and wondering which vSAN architecture aligns best with your environment and hardware? Look no further! This blog post for you.

 VMware vSAN 8 brings forth a revolutionary leap in storage technology with its Express Storage Architecture (ESA). This optional, alternative storage architecture is meticulously crafted to complement vSAN's original storage architecture (OSA), delivering unparalleled performance, scalability, resilience, and advanced data services. Join us in this blog as we dissect the disparities between these two architectures, shedding light on how ESA leverages contemporary hardware to meet the evolving demands of present and future workloads.

Key Differences Between ESA and OSA

Architectural Design

  • Original Storage Architecture (OSA):
    • Two-Tier Design: Combines cache and capacity devices.
    • Device Compatibility: Supports a wide range of storage devices including SATA, SAS, and NVMe.
    • Flexibility: Suitable for various hardware configurations, allowing custom-built setups with certified devices.
  • Express Storage Architecture (ESA):
    • Single-Tier Design: Optimized for high-performance NVMe-based TLC flash devices.
    • Device Compatibility: Requires vSAN ESA certified NVMe devices, ensuring consistent performance.
    • Performance Optimization: Tailored for NVMe devices, providing superior performance and lower latency.
    • Deployment: Available only on vSAN ReadyNodes, ensuring a streamlined and optimized setup.

Performance Enhancements

  • Log Structured File System: ESA uses a new file system that enables the use of RAID-6 at the performance level of RAID-1, a significant improvement over the OSA's need to balance between RAID configurations based on capacity and performance needs.
  • Compression and Data Services: ESA offers per-virtual-machine compression that occurs before data traverses the network, enhancing throughput and reducing networking overhead. This architecture supports a high data reduction ratio, potentially achieving up to an 8:1 compression for every 4KB block written.
  • Snapshot Efficiency: ESA's native snapshot engine is vastly more efficient, providing up to 100 times faster snapshot consolidation times and enabling new use cases through enhanced backup APIs.

Capacity and Cost Efficiency

  • Removal of Cache Devices: ESA eliminates the need for dedicated cache devices, utilizing all available device capacity for the vSAN datastore. This change reduces write amplification and latency, while also simplifying the storage configuration.
  • Flexible RAID Configurations: ESA supports RAID-5 in smaller clusters with a minimum of 3 nodes, and offers more capacity-efficient stripe sizes for larger clusters. This flexibility, combined with the removal of cache devices, significantly lowers the cost per GB for vSAN clusters.

Security Improvements

  • Enhanced Encryption: In ESA, data encryption occurs at the host level, ensuring data is encrypted once at rest. This approach reduces CPU overhead and minimizes I/O amplification related to encryption processes. ESA also supports layering data encryption on top of vSAN datastore encryption for added security.

Networking Requirements

  • Higher Minimum Bandwidth: ESA mandates a minimum of 25Gbps networking, compared to OSA's 10Gbps. This requirement ensures that the high-performance capabilities of NVMe devices are fully utilized, offering superior performance and reliability.

Hardware Choices and Requirements


vSAN 8.0 ESA

vSAN 8.0 OSA

Storage Device Minimums



Hardware Choices

vSAN ESA certified NVMe devices

SATA, SAS, NVMe certified devices

Cache Device Requirements

No Cache Devices

1 Cache Device per Disk Group


ReadyNodes Only

ReadyNodes or custom builds with certified devices

Networking Minimums

25Gbps minimum

10Gbps minimum

The decision to require a 4-device minimum for ESA aims to ensure high performance and availability, leveraging the capabilities of NVMe devices for consistent performance and reduced latency. The move to 25Gbps networking further guarantees that the enhanced performance of these devices is fully realized.

VMware vSAN 8's Express Storage Architecture (ESA) marks a significant leap forward in storage technology, optimizing for high-performance NVMe-based TLC flash devices and providing unmatched performance, scalability, and efficiency. While the Original Storage Architecture (OSA) continues to support a broad range of hardware configurations, ESA represents the future of vSAN, designed to meet the demands of modern workloads with revolutionary advancements in storage performance and efficiency. Customers can confidently choose the architecture that best suits their needs, knowing that VMware supports both OSA and ESA, ensuring flexibility and longevity in their storage solutions.


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