Quick Reference Information Related to VMware VSAN

Hey Guys, I had created this blog post for sharing a quick reference information about VSAN and yes this can be used for a quick refresh before your interviews as well πŸ™‚

It could be a bit lengthy being VSAN is a vast topic, but had tried to keep it shorter by giving relevant information’s.

So let’s start with it.

VSAN Basics:

VSAN can be (Hybrid or All Flash) environment
VSAN = Cache Device + Capacity Device
Capacity Tier: Must have at least 1 Capacity Device
Cache Tier: Must have at least 1 Cache Device
All Flash – write Cache only
Hybrid – For both write and read cache is available.
Each host in the VSAN Cluster can have 5 Disk Groups Max and Each Disk Group with 1 SSD + 1-7 HDD’s.

VSAN Network:

Atleast 1 GB dedicated Network in Hybrid Configuration
10 GB for All Flash Configurations
VSAN supports Standard Switch and Distributed Virtual Switch (DVS) both.
Benefit of using DVS is having support of Network IO Control.
For VSAN Communicated Network, VMkernel Port group need to be created.
VSAN also supports LACP – NIC Teaming
From VSAN 6.6 and higher , there is no more need of multicast.

VSAN Hardware Requirement:

Minimum 3 hosts (VSAN Ready Nodes) are required for creating VSAN Cluster.

VSAN Storage:

VMware VSAN uses Storage Policies Based Management (SPBM).
Distributed RAID.
VM availability and Performance defined on per-VM basis through the use of Storage Policies.

What is Failure to Tolerate (FTT) in VSAN:

FTT is required to determine how many nodes or disk failures can VSAN cluster survive.
Below have shown what are the requirements, performance and storage impact of FTT configuration.

Failure to Tolerate (FTT)= 1
100 GB VMDK = 200 GB Consumed Physically
Minimum Hosts = 3
Performance = High

Failure to Tolerate (FTT) = 2
100 GB VMDK = 300 GB Consumed Physically
Minimum Hosts = 4
Performance = High

Raid 1
Minimum Hosts = 3

Raid 5
Minimum Hosts = 4

Raid 6
Minimum Hosts = 6

Steps for configuring 2 hosts VSAN Cluster for your lab environment:

  1. Configure VMkernel Port for VSAN on Host
  2. Create Cluster
  3. Add hosts to the cluster
  4. Disable HA before configuring VSAN
  5. Configure VSAN on cluster
  6. Select Configuration Type
  7. Single Site Cluster
  8. Two Hosts VSAN Cluster
  9. Stretched Cluster
  10. Select the Disk to claim for Cache and Capacity
  11. Create Fault Domain
  12. Click Finish

Types of VSAN Maintenance/ VSAN data Migration mode:

1)Evacuate all data to other ESXi hosts
2)Ensure data accessibility from other ESXi hosts
3)No data evacuation

Further information about VSAN Maintenance Mode is available in Below link:


Reasons for Disabling HA, Prior to configuring VSAN

In a VSAN environment , vSphere HA agent communicates over VSAN Network.

In the event of Failure , we want vSphere HA and VSAN hosts to be part of same network partition. This avoids possible conflicts  when vSphere HA & VSAN observes different partitions when failure occurs, with different partition holding subsets of storage components & objects.

Scenario of having two different networks for VSAN and Host Management

It is recommended to change the vSphere HA default isolation address to VSAN Network IP address.

Reason: By default, isolation address is of Management Default Gateway. But if there is network issue in VSAN Network, host is isolated from VSAN, but HA will not trigger as there is no problem with the Host Management Network.

How to change Default Isolation Address:

You can change the default isolation address by going to advanced options of vSphere HA.

Information and Configuration of HA in VSAN Cluster

vSphere HA hosts does not use VSAN datastores for vSphere HA Heart Beat

vSphere HA isolation response in the event of host isolation should be power off and restart VM’s

Recommended ratio for cache is 10 %of capacity in Hybrid Environment

Maximum Number of Components per Host limit is 9000

In the event of Host failure, VSAN will wait for 60 Mins for hosts to come back online. Else it will start rebuilding data/parity.

Data Deduplication and Compression are only available in all Flash Scenarios



VMware VSAN 6.7 U1 Deep Dive Book

Happy Learning Guys  πŸ™‚

Feel free to like, comment and share.

I would be more than happy to reply to your queries.

Rajesh Poojary

Where to find me πŸ™‚

Twitter : https://twitter.com/CloudBicepsGuy

Mail : CloudBiceps@gmail.com


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