VMware vSAN 8 introduces the revolutionary Express Storage Architecture. This is an alternate storage architecture to the vSAN original storage architecture, which is also included in vSAN 8. The vSAN Express storage architecture will provide superior levels of performance, scalability, resilience, and data services when running on certified hardware in approved vSAN Ready Nodes.
What makes vSAN ESA unique?
At a high level, the original vSAN storage architecture was a two-tier architecture designed to support a diverse set of older storage devices, whereas the vSAN Express Storage Architecture in vSAN 8 is a single-tier architecture optimized for high performance NVMe-based TLC flash devices for both on-premises environments and hyperscale public clouds. With vSAN 8, VMware allows you to choose which architecture best suits your existing hardware while deploying new clusters with unparalleled levels of performance.
Performance -
Previously, when determining whether to use RAID 1, RAID 5, or RAID 6, the vSAN original storage architecture required careful planning. Workloads requiring maximum capacity would select RAID 5/6, whereas workloads requiring maximum write performance would select RAID 1. vSAN Express Storage Architecture employs a new log-structured file system that enables the cluster to store data using RAID-6 while maintaining RAID-1 performance. Compression is now per virtual machine and will compress data before it traverses the network, allowing for higher performance with fewer networking overhead. The new native snapshot engine in vSAN ESA is highly scalable and efficient.
Capacity Improvements -
vSAN Express Storage Architecture allows the cluster to store data using RAID-6 at the performance of RAID-1. RAID 5 can now be configured in a 2+1 or 4+1 configuration. This adds RAID 5 support to clusters as small as three nodes while allowing bigger clusters to use a more capacity-efficient stripe size. Dedicated cache devices are no longer required with vSAN 8 ESA. The new log-structured file system and IO path optimizations to the write path have been implemented to minimize write amplification and latency even further. The removal of the disc groups concept has the further benefit of limiting drive failures to a single storage device. The capacity of all devices is usable by the vSAN datastore in the absence of cache devices. The ability to employ RAID 5/6 at all times, combined with the elimination of the need for cache devices, can considerably lower the cost per GB for VMware vSAN clusters. New strategies are in place to boost the compression feature's potential data reduction to as high as an 8:1 compression ratio for every 4KB block produced, which is a 4x improvement over the original storage architecture. These new capacity savings are implemented in such a way that both money and performance are saved.
Security Improvements -
The vSAN Encryption process is moved higher in the stack to the host where the virtual machine lives in vSAN Express Storage Architecture. Data only needs to be encrypted once at rest; there is no need to potentially decrypt and re-encrypt as was required in the original storage architecture when data needed to be decrypted to perform compression while migrating from cache to capacity devices. This modification reduces the CPU cost of encryption as well as the I/O Amplification required to employ encryption. For enhanced protection, data encryption can be stacked on top of vSAN datastore encryption.
Snapshots differences -
The snapshot architecture used in prior vSAN editions can be regarded of as an improved version of the redo-log-based snapshot architecture that has been a part of vSphere for many years. Previously, vSAN 6 introduced the “vsanSparse” snapshots to alleviate some of the technical implications of traditional, redo-log based snapshots. This enhancement did not address all issues, such as sluggish snapshot consolidation times, performance degradation during snapshot operations, or even long-term retention. The introduction of a whole new native snapshot mechanism in vSAN ESA allows for faster snapshot operation speeds (100x faster consolidation) and opens up potential new use cases. Because these new snapshots are accessible via backup APIs, they can be used as a drop-in replacement for Virtual machine backup and replication products.
Disk Groups vs. Pools -
Dedicated cache devices are no longer required with vSAN 8 ESA. The new log-structured file system and IO path optimizations to the write path have been implemented to minimize write amplification and latency even further. This has the extra benefit of not affecting the remaining storage devices in the host if one of the storage devices fails. The capacity of all devices is usable by the vSAN datastore in the absence of cache devices.
Hardware Choices -
A 4 device minimum was chosen at this time to enforce a minimum expected performance outcome as well as to enhance availability.
vSAN 8 Express Storage Architecture (ESA) represents a significant leap forward in storage efficiency and performance for virtualized environments. With cluster-level deduplication and compression, enhanced erasure coding, intelligent caching mechanisms, and integrated data protection features, vSAN 8 ESA elevates the storage capabilities of VMware's vSAN platform.
As storage requirements continue to grow in virtualized environments, vSAN 8 ESA stands as a powerful solution that empowers organizations to maximize their storage resources and unlock the full potential of their virtualized infrastructure.
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