# vmware-design math – calculate vsan requirements

Here’s a math question based on the vsan design and sizing guide

Customer wants to deploy 100  virtual  machines in a hybrid Virtual SAN 6.0 cluster, disk format v2
Each virtual  machine requires  2  vCPU,  8GB  of  memory  and  a  single  100GB  VMDK.
Snapshots are not used. Customer expect a vCPU-to-core ratio of 5:1

Customer has acquired 3 Physical hosts, design should incorporate that if a single host fails all  VMs will be able to run on just two hosts

The following disk sizes have been choosen
900GB SAS 10K RPM Magnetic Disk
100GB SAS SSD SSD Flasg Disks

Estimation is that the Guest OS and application will consume 50% of the storage. FTT = 1
However, the requirement is to have enough storage to allow VMs to consume 100%  of the storage eventually.

First work out the following ( you are expected to know the design guidelines for overhead, slack space, cache size, etc…
Total CPU Requirements:
Total Memory Requirements:
Total Storage Requirements (with FTT) + VM Swap (with FTT):
Estimated Storage Consumption (without FTT)for cache calculation:
Cache Required (of Estimated Storage Consumption):
Total Storage Requirement  + Slack space:
Estimated on-disk format overhead:
Virtual SAN CPU overhead:
Total vm components:

Provide answers to the following questions;
What is the total SSD required for cache?
What is the total requirement for HDD?
How many disk groups are required?
Including van overhead, how many cpu cores are required per host, taking into account 1 host is allowed to fail?
Including van overhead, how much memory is required on each physical host? (TPS, not included, assume  0 memory overcommitment)
What is the total SSD required on each physical host?
What is the total required on each physical host?

For the answer, and calculations see page 61 of the VSAN_Design_and_Sizing_Guide.pdf
http://www.vmware.com/files/pdf/products/vsan/VSAN_Design_and_Sizing_Guide.pdf