Stretched Cluster vs Fault Domains

[9lz]

Hello,

I struggle to understand when to recommend Stretched Clusters and when to recommend using Fault Domains. Anyone got a good comparison? I know that Fault Domains require <1ms latency between hosts and Stretched Clusters require <5ms latency. Some customers wants to use Fault Domains between three bulidings instead of Stretched Cluster as this can be accomplised with a cheaper vSAN license.

Thanks.

[depping · Accepted solution]

I have customers doing that as well, even between 4 or 5 buildings. Stretched clusters are used when latency is between 1ms and 5ms round trip. Fault domains can be used for <1ms. Other than that there are no guidelines. If you have 3-4 buildings with a high bandwidth low latency connection then I would also go for fault domains to be honest.

[9lz]

Thanks depping! This is documented in the VMware® vSAN™ Network Design document under 5.7 Corner Case deployments, but it doesn't really list any pros and cons with either solution. I guess ready localty with Stretched Clusters may be an advantage, but I guess it's not enough to defend the license cost by itself. The witness appliance can be a pro or a con, depending on what your 3rd site is able to run. Stretched Clusters may also be simpler to understand and manage since they are diveded into two equal data sites instead of three+ with Fault Domains? So that you can calculate to have at least 50% free capacity in case one site fails.

[CyberNils]

Hi,

I know this is an old post, but my customers are still considering this. Do you know if they can downgrade their Enterprise licenses to Advanced licenses or do they have to buy new Advanced licenses which cost a lot more than SnS? Thanks.