Welcome Readers!
In this blog, we will be understanding about VMware High Availability and Fault Tolerance features offered by vSphere.
High Availability:
In HA, when the host crashes or fails, the VMs on it gets restarted on another host within the same cluster. Hence, there is a very small downtime which is only related to the time taken for the VM to restart.
HA is a completely automated process and does not need any administrator's interference as there is no time to recover machine if host is about to crash.
No passive standby ESXi host is required neither any extra VM. The VM where the host is crashing, it can restart on any other running host in same cluster.
Pre-requisite for HA configuration:
vCenter Server configured for the enviroment
Cluster
Shared Storage
Fault Tolerance:
Aim of FT is similar to HA, but in terms of availability, it provides 0% downtime and full availability as machine does not go down or reboot.
This is meant for mission critical applications/servers. Ex., Robotic Surgery Arm, Auto-Pilot system in aircraft, etc. (where impact can lead loss of life)
VMware lockstep technology is used in FT
With FT, a secondary VM is created on another host using distributed resources scheduler. This VM is exact replica of the primary VM.
(Primary & Secondary work in lockstep, i.e., the lockstep technology captures the current state & event of primary VM and send them to secondary one. If primary goes down, instantly secondary VM takes over and continue operations)
FT requires an extra bandwidth for syncing of state and events.
Difference between vMotion/HA/FT
Thats all for this blog now!
Happy Reading! Happy Learning!
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