If you have been managing vSAN environments for a while, you know that the holy grail of storage is maximizing your capacity reductions without sacrificing a single drop of virtual machine performance. Well, I have some excellent news to share: with the release of vSAN in VCF 9.1, the platform is taking space efficiency to entirely new levels.
Between a major under-the-hood engine swap for compression and the General Availability (GA) of Global Deduplication, vSAN 9.1 is built to drive your storage costs down dramatically.
Let’s dive into exactly what is changing and why it matters for your data center.
Farewell LZ4, Hello Zstandard (ZSTD)
Historically, data compression in vSAN (both OSA and ESA) relied on the LZ4 algorithm. LZ4 was a solid workhorse and it was lossless, incredibly fast, and very light on the CPU. That low overhead was especially critical for the older vSAN OSA architecture. However, the tradeoff for that speed was a lower overall data reduction rate compared to other modern algorithms.
Zstandard (ZSTD)
With vSAN in VCF 9.1, ZSTD is taking the reins. It is a highly versatile and tunable lossless compression algorithm that delivers noticeably higher compression ratios than LZ4 while maintaining impressive performance and modest CPU usage. Because the newer vSAN Express Storage Architecture (ESA) has such massive performance capabilities, this algorithmic swap effectively reduces your storage footprint with a negligible impact on VM performance. ZSTD has been specifically tuned by the engineering team to find the absolute sweet spot between performance, data reduction, and physical resource consumption.
What This Means for Your Workloads
Because audio, video, and image files are usually already compressed by their native file formats, the biggest winners here are your structured data workloads. This new algorithm is absolutely ideal for:
- Databases (where patterns, integers, dates, and repeatable keys are highly prevalent)
- Virtual Desktop Infrastructure (VDI)
- Backup data repositories
While reduction rates always vary based on the specific characteristics of your data, you can expect to see up to a 50% improvement in data reduction from compression alone. Telemetry from older ESA environments often showed an average compression ratio of around 1.5x. With ZSTD, those averages are projected to push closer to 2.0x!Squeezing Every Last Byte: Inside vSAN 9.1’s Massive Space Efficiency Upgrades
Always-On Compression & Global Dedup
One of the most significant operational shifts in this release is that compression is now an always-on feature of the cluster. It is no longer managed as a cluster service or a policy rule, meaning it cannot be disabled.
When you pair this always-on, high-efficiency ZSTD compression with the official GA of vSAN Global Deduplication, you get a storage system that works relentlessly in the background to minimize your physical footprint.
You can monitor all of this in the updated UI. Check out the new “Effective Capacity” view to see discrete statistics for both deduplication and compression ratios. Keep in mind: while it is fun to look at those individual numbers, the ultimate metric to watch is your overall “Data Reduction Ratio.”
Upgrading to 9.1: Greenfield vs. Brownfield
If you are planning an upgrade, there are a few important things to know about how this rolls out.
First, you will need to be running both vSAN 9.1 (or newer) and vCenter 9.1 (or newer). Upgrading an existing cluster will require a Disk Format Change (DFC) to the latest vSAN format version.
Once your upgrade and the DFC are complete, the cluster-level compression is enabled by default. Here is how your data is handled:
This is an incredibly exciting, iterative step in a much larger, ongoing effort to optimize storage efficiency in vSAN. I cannot wait to see how these new algorithms shrink the storage footprints in my own environments!
Final Thoughts
Honestly, vSAN 9.1 is the space-saving upgrade we’ve all been waiting for. By swapping in always-on ZSTD compression and rolling out Global Deduplication, VMware is basically handing us free storage capacity on the hardware we already own. The fact that the upgrade is completely painless—and that your existing data literally shrinks itself in the background over time as it rewrites—is just brilliant. In my book, if you want to stretch your budget and get more mileage out of your racks, pulling the trigger on 9.1 is an absolute no-brainer!
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Disclaimer: Please note that the views expressed in this blog are solely my own and should be treated as personal opinions. This content does not hold any legal or authoritative standing.