Read on:
VMware for Beginners – vMotion and DRS: Part 11
VMware for Beginners – vSphere HA Configuration: Part 12(a)
VMware for Beginners – vSphere HA Configuration: Part 12(b)
VMware for Beginners – vSphere HA Configuration: Part 12(c)
VMware for Beginners – What is vSphere Proactive HA?: Part 13
VMware for Beginners – What is VMware vSphere Fault Tolerance and How Does it Work?: Part 14(a)
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In the last post, we started the subject vSphere Fault Tolerance with the first part. This is the second part of vSphere Fault Tolerance(FT).
What will we discuss in this vSphere Fault Tolerance part two?
- How to configure vSphere Fault Tolerance?
- Pros and Cons of vSphere Fault Tolerance
How to configure vSphere Fault Tolerance
Before enabling vSphere Fault Tolerance in your VMs, you need to create a network that will support this feature and is used for VMs sync.
We need to create a VMkernel for Fault Tolerance Logging.
Note: We have already discussed in previous articles how to create a VMkernel.
Select your ESXi host, and in the Configure tab select VMkernel Adapters and click Add Networking.
Then select the VMkernel Network Adapter.
Next, select the Virtual Switch that this VMkernel will be using. In this case, we will use the Switch that we are using for Storage(Switch1).
Note: Since we did not learn about Distributed Virtual Switches, we will use a Standard Switch.
Add a name for the Portgroup(not mandatory you can use the default) and enable the vSphere Fault Tolerance service.
Next, add an IP address for your vSphere Fault Tolerance network.
Note: You can isolate the network using VLANs or a different subnet.
Next, check all the configuration information; if all is ok, click Finish.
Note: As we learned in previous articles, the above process must be done in all ESXi hosts in the Cluster.
Now that we have created our vSphere Fault Tolerance network, we can enable it on your Virtual Machines.
Select the Virtual Machine that you want to enable vSphere Fault Tolerance and with a right click in the VM menu, select the Fault Tolerance tab, and then Turn On Fault Tolerance.
Select the Datastore for the Seconday VM. As we learn in the first part of this article, Datastore needs to be a shared Datastore and a different Datastore where the VM is stored.
Next, select the ESXi host in which you place this Secondary VM.
Double-check the information and click Finish.
As we can see in the next image, vSphere Fault Tolerance created a Secondary VM.
These two VMs for which we enabled vSphere Fault Tolerance are now Virtual Machine FT. Both are protected from any failures again. In case of any failures, the Secondary VM will take over and continuously work without downtime in the Guest OS or Applications.
If you check the Fault Tolerance options in the Virtual Machine, you see some management options to check the Fault Tolerance.
For testing, failover to check if vSphere Fault Tolerance will work in case VM fails. Or migrate the Secondary VM to another ESXi host. You can also suspend or stop vSphere Fault Tolerance for this VM.
As discussed in the first part of vSphere Fault Tolerance, this High Available vSphere service is essential for your business continuity.
vSphere Fault Tolerance (FT) can be used when an application or a Guest OS cannot be clustered. FT effectively provides high-availability for applications and VMs that cannot be clustered due to hardware or software limitations.
When using FT, you can create a “live shadow instance” of the primary VM and run both copies simultaneously. If one of the machines fails, the other will take over. This eliminates the need to manually manage and configure failover processes while providing increased reliability, improved performance, and cost savings.
It is important to note that specific workloads are not eligible for FT. Let us resume the pros and cons when using vSphere Fault Tolerance.
Pros and Cons of vSphere Fault Tolerance
VMware vSphere Fault Tolerance provides continuous availability for virtual machines. Like any technology, Fault Tolerance has both pros and cons.
Pros of vSphere Fault Tolerance:
The primary benefit of using vSphere Fault Tolerance (FT) is its ability to provide continuous uptime in case of hardware or software failure. With vSphere Fault Tolerance, users can keep their applications running without experiencing any downtime due to unexpected outages. Additionally, vSphere Fault Tolerance offers many performance benefits, including:
- Increased Reliability: By providing automated failover in the event of hardware or software failure, vSphere Fault Tolerance allows applications to continue running without disruption
- Improved Performance: Through its live shadow instance of the primary virtual machine, vSphere Fault Tolerance provides faster response times and improved application throughput
- Cost Savings: By manually eliminating the need to manage failover processes, vSphere Fault Tolerance reduces the cost of IT personnel to maintain operations. Additionally, by reducing downtime, vSphere Fault Tolerance helps to minimize lost revenue due to outages
- Reduced Complexity: vSphere Fault Tolerance simplifies the process of configuring and managing application availability, allowing users to focus on core tasks and activities
Overall, vSphere Fault Tolerance provides a reliable and cost-effective solution for ensuring the availability of applications and services. By providing a live shadow instance of a virtual machine, vSphere Fault Tolerance ensures that any outages are quickly mitigated and that applications remain operational.
Additionally, it offers a number of performance and cost benefits to help organizations maximize the return on investment of their IT infrastructure.
Cons of vSphere Fault Tolerance:
The main disadvantage of vSphere Fault Tolerance (FT) could be its increased resource usage. Since FT creates a live shadow instance of the primary VM, it requires double the resources usually needed for a single VM. This can be a concern if resources are limited or multiple FT-protected VMs run on the same host.
Additionally, FT imposes two limits that must be considered: the maximum number of Fault Tolerant VMs allowed on a host in the Cluster (the default is 4) and the maximum number of FT VMs per host (which is unlimited but can vary depending on the workload).
Limited 4 Virtual Machines per ESXi host and a maximum of 8 vCPUs per ESXi host can use vSphere Fault Tolerance. If your VM has multiple vCPUs, you need to reduce it to 2 or 8 vCPU to use Fault Tolerance.
Furthermore, vSphere Fault Tolerance cannot protect specific virtual machines with raw device mapping, memory reservations, and more than four virtual CPUs. Also, when using FT, some features, such as snapshots, DRS, and High Availability, may not be available or have limited functionality.
Moreover, troubleshooting FT-protected VMs may be more complicated than other VMs due to the complex architecture of Fault Tolerance. Finally, vSphere Fault Tolerance requires additional storage space for the shadow VM, which can also be a limitation.
Conclusion
vSphere Fault Tolerance is a powerful feature of VMware vSphere that provides continuous availability for virtual machines. By maintaining a synchronized copy of the VM on a secondary host, Fault Tolerance ensures that critical applications and services remain available to end-users at all times, even during a primary VM failure.
While Fault Tolerance offers many benefits, there are also several restrictions and limitations to consider, such as the requirement for compatible hardware and software, limited virtual machine configurations, and increased network and storage requirements.
By carefully evaluating the pros and cons of vSphere Fault Tolerance in your environment, you can decide whether to implement this feature and how best to configure it to meet your needs.
Read more on our VMware for Beginners series:
VMware for Beginners – Overview of vSphere: Part 1
VMware for Beginners – vSphere Installation Requirements: Part 2
VMware for Beginners – How to Install vSphere: Part 3
VMware for Beginners – vSphere Networking: Part 4
VMware for Beginners – vSphere Datastores: Part 5
VMware for Beginners – vSphere Virtual Machines: Part 6
VMware for Beginners – How to Install vCenter: Part 7
VMware for Beginners – Datacenter and Clusters: Part 8
VMware for Beginners – How to Create and Configure iSCSI Datastores: Part 9(a)
VMware for Beginners – How to Create and Configure iSCSI Datastores : Part 9(b)
VMware for Beginners – How to Create NFS Datastores: Part 10(a)
VMware for Beginners – How to Create NFS Datastores: Part 10(b)
