First of all, I recommend everyone to check out this link.
It has lots of good information for VCAP – DCA exam.
I’m going to put some conclusion I made from my point of view. Please let me know if there are any problems or mistakes.
Objective 4.2 – Deploy and Test VMware FT
Identify VMware FT hardware requirements
Identify VMware FT compatibility requirements
Skills and Abilities
Modify VM and ESX/ESXi Host settings to allow for FT compatibility
Use VMware best practices to prepare a vSphere environment for FT
Configure FT logging
Prepare the infrastructure for FT compliance
Test FT failover, secondary restart and application fault tolerance in a FT Virtual Machine
vSphere Availability Guide
Few things we need to learn for this Objective.
1. VMware FT record some of important activities from primary and pass to secondary VM to execute. It means not all activities will be past through to secondary VM.
The primary VM and secondary VM stay in sync with each other by using a technology called Record/Replay that was first introduced with VMware Workstation. Record/Replay works by recording the computer execution on a VM and saving it as a log file. It can then take that recorded information and replay it on another VM to have a replica copy that is a duplicate of the original VM.
Instead, only non-deterministic events are recorded, which include inputs to the VM (disk reads, received network traffic, keystrokes, mouse clicks, etc.,) and certain CPU events (RDTSC, interrupts, etc.). Inputs are then fed to the secondary VM at the same execution point so it is in exactly the same state as the primary VM.
The primary VM transmit Network traffic+disk traffic+overhead (20%) to secondary VM. That’s why it requires dedicated Gbit nic.
2. There lots of comparison between FT,HA and MCSC. When and where shall we use which tech?
FT is more focus on short recovering period for host failure. It doesn’t require VM to restart (like HA) and it also can work with different OS other than Microsoft(MSCS can only work for MS OS). It’s easy to setup and easy to use.
Objective 4.3 – Configure a vSphere Environment to support MSCS Clustering
Identify MSCS clustering solution requirements
Identify the three supported MSCS configurations
Skills and Abilities
Configure Virtual Machine hardware to support cluster type and guest OS
Configure a MSCS cluster on a single ESX/ESXi Host
Configure a MSCS cluster across ESX/ESXi Hosts
Configure standby host clustering
Setup for Failover Clustering and Microsoft Cluster Service
• Product Documentation
• vSphere Client
With MSCS, it has capability to monitor application level to let secondary machine to take over. It’s faster than HA and can understand how application works.
In a server cluster, each server owns and manages its local devices and has a copy of the operating system and the applications or services that the cluster is managing. Devices common to the cluster, such as disks in common disk arrays and the connection media for accessing those disks, are owned and managed by only one server at a time. For most server clusters, the application data is stored on disks in one of the common disk arrays, and this data is accessible only to the server that currently owns the corresponding application or service.
The following environments and functions are not supported for MSCS setups with this release of vSphere:
- Clustering on iSCSI, FCoE, and NFS disks.
- Mixed environments, such as configurations where one cluster node is running a different version of ESX/
- ESXi than another cluster node.
- Use of MSCS in conjunction with VMware Fault Tolerance.
- Migration with vMotion of clustered virtual machines.
- N-Port ID Virtualization (NPIV)
- With native multipathing (NMP), clustering is not supported when the path policy is set to round robin.
- You must use hardware version 7 with ESX/ESXi 4.1.