High availability, Fault Tolerance, Storage APIs

High Availability (HA)

automated process for restarting VMs that were running on an ESXi host at a time of complete server failure
VMs are migrated to an ESXi host that is part of the HA-enabled cluster (does not use vMotion!!)
Intended to address unplanned downtime, not planned outages
Improved in v5

1. scalability (up to 512 VMs per host and 3000 VMs per cluster)
2. integrates more closely with DRS, giving Ha greater ability to restart VMs in the event of a host failure
3. rewrite of the architecture to Fault Domain Manager, eliminating many of the contraints in earlier versions

by default, vSphere HA does not provide failover in the event of a guest OS failure, but it can.
Remember that HA will have service interruptions. If vSphere HA restarts the VM, the applications or services provided by that VM are unavailable during the restart

vSphere Fault Tolerance (FT)

Even greater level of high availability than HA can provide.
Eliminates any downtime in the event of a host failure
uses vLockstep technology
utilizes a mirrored secondary VM on a separate physical host that is kept in lockstep with the primary VM.
If the physical host on which the primary VM is running fails, the secondary VM can immediately step in and take over without any loss of connectivity.
Also, if the physical host on which the secondary VM is running fails, the mirrored secondary VM will be automatically recreated on another host.
In the event of multiple host failures, vSphere HA will reboot the primary VM on another available server and recreate the secondary VM
In this version, vSphere FT can work in conjunction with vMotion and is integrated with DRS, but it does require EVC

vSphere Storage APIs for Data Protection and VMware Data Recovery

Two key components:

1. vSphere Storate APIs for Data Protection (VADP)
2. VMware Data Recovery (VDR)

VADP is a set of APIs that backup vendors leverage to provide enhanced backup functionality of virtualized environments
enables functionality like file-level backup and restore; support for incremental, differential, and full-image backups
supports multiple storage protocols
provides for native integration with backup software
NOT a backup solution, it just provides the framework for making backups possible.
VMware Data Recovery (VDR) is VMware's backup tool that leverages VADP to provide a full backup solution for smaller vSphere environments