Why All-Flash VSAN Really Has a Better TCO

By Jason Massae - 1.6.16

In 2013, when VMware first released Virtual SAN (VSAN), Micron saw a significant opportunity to leverage solid state drives (SSDs) to maximize VSAN’s performance and functionality while extending additional benefits that are unattainable with standard HDDs. With the first release, we demoed an unsupported, all-SSD configuration at VMworld 2014 and saw a 10x performance increase compared to HDDs. Keep in mind that with that initial release, it was not optimized for flash like the current versions. Nevertheless, the gains to be realized were obvious.

Fast forward to the current release (coming soon), which fully supports and is optimized for all-flash VSAN, and the performance and benefits are far greater. The all-flash VSAN configurations can realize upwards of 100K IOPS per node while maintaining sub-millisecond latencies. Additionally, they are easier to setup, have reduced complexity in the environment and are extremely scalable. What does all this mean? It means administrators, data center owners, customers, etc. can now get consistent and predictable performance without having to increase complexity or purchase additional expensive flash arrays that can’t scale like VMware’s VSAN.

With Micron’s enterprise SSDs now in the 60 cents/GB range, the only potential cost alternative is a 7200 RPM drive. This option is only for capacity functionality as any other performance functionality requirements negate its value. SSD’s substantial performance over HDD is reason enough to go with an all-flash VSAN – not to mention other benefits. It’s these additional, less obvious benefits that add to the total cost of ownership (TCO) of all-flash VSAN.

Reduced Power Consumption

One of these less obvious benefits that add to TCO is power consumption. An SSD uses less power at idle and under load. We did a simple test with a server at idle and the exact same server with all SSDs used ~70 watts while the all-HDD server used ~100 watts. This may seem negligible but when you’re talking about tens, hundreds, or even thousands of servers, these power numbers quickly add up. The all-flash servers use less power and generate less heat. This can be critical for data centers and lead to very little to no overhead in their cooling system. Historically, data centers were not able to add additional resources solely because they didn’t have the cooling capacity. Upgrading to SSDs allows them to reduce cooling and power usage, thereby enabling additional resources.

Eliminate Vibration

Vibration is another factor many don’t realize may cost them performance as well as money. I’ve spoken with engineers from VMware as well as customers that continuously have to replace HDDs in harsh environments as a direct result of vibration. With SSDs, vibration issues are completely eliminated. Now, regardless of the environment – from offshore oil drilling rigs, Nascar mobile data centers or even a noisy data center – vibration is no longer going to cost you. There’s a great video someone did on YouTube showing a guy in a data center yelling at an HDD array. While he did the test, he ran d-trace to show the individual drive’s performance and latency. When he yelled at the array, the latency severely spiked! Did he damage the drives? Who knows? Although I sure wouldn’t recommend doing it on a production system! The idea here is there are other environmental impacts that could be causing performance issues or premature drive failures, resulting in higher maintenance costs.

What’s the point to all this? If you think a hybrid VSAN is less expensive or a better value, you’d better look deeper at the overall value and benefits of an all-flash VSAN. It’s much greater than you realize!

Amit Gattani

Jason Massae