vSAN Memory Consumption Calculator

The vSAN Memory Consumption Calculator has been updated on 19-01-2021 to reflect vSAN 7.x after the KB has been updated and I got some messages that the calculator was not up-to-date anymore.

Disclaimer !! This calculator is officially not supported by VMware, please use this calculator for indications only. Please use the official vSAN sizer at https://vsansizer.vmware.com/ for vSAN sizing.

I ran into a strange issue today, a host was consuming way to much of RAM while running a single VM running on it. And that single VM was only configured with half of the RAM of the host?!? After some basic troubleshooting a colleague (thanks Satish) pointed me to the KB article KB2113954 which explained the issue.

vSAN Memory

The host in question was configured with 128GB of RAM and had 4 disk groups with 7 large capacity disks. If you do the math it required 48GB of RAM to run this vSAN configuration. In other words, it explained what we saw! vSAN was gobbling up more RAM than was anticipated!

To calculate vSAN memory consumption you use this equation:

vSANFootprint = HOST_FOOTPRINT + NumDiskGroups * DiskGroupFootprint

DiskGroupFootprint = DISKGROUP_FIXED_FOOTPRINT + DISKGROUP_SCALABLE_FOOTPRINT + CacheSize * CACHE_DISK_FOOTPRINT + NumCapacityDisks * CAPACITY_DISK_FOOTPRINT

Easy right? Well let me make it even easier for you:
 

All Flash vSAN Memory Consumption Calculator

 
 

Hybrid vSAN Memory Consumption Calculator

 
 
* vSAN scales back on its memory usage when hosts have less than 32GB of memory. Source: Link

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