vSAN Operations Guide: Managing Fault Domains

If your vSAN cluster includes several racks or blade server enclosures, fault domains let you safeguard against rack or enclosure failure. Fault domains can be formed, and each fault domain can have one or more hosts.

One or more virtual SAN https://fsecan.ca/blog/index.php?entryid=305163 nodes are classified into the fault domain according to where they are physically located in the data center. When properly set up, fault domains allow VSANs to endure both host, capacity device, network connection, and network switch failures as well as the failure of whole physical racks.

The number of failures that the VM permits determine the primary degree of permissible policy failures for a cluster. If the basic fault tolerance level is set to 1 (PFTT=1) while configuring the VM, vSAN will let a single failure of any kind affect any component inside the fault domain, along with the failure of the entire rack.

Replicas and witnesses are deployed in various fault domains when you set the rack fault domains and assign a new virtual machine. For instance, vSAN needs at least 2*n+1 fault domains in the cluster if the primary fault tolerance level is set to N (PFTT=n) in the VM storage policy. This strategy places copies of the corresponding virtual machine objects in different racks when virtual machines are deployed in a cluster with failure domains.

To support PFTT=1, at least 3 fault domains are needed. Configure the cluster with four fault domains or more for the best results. Similar restrictions apply to a cluster with 3 fault domains as they do to a cluster with three nodes, such as the inability to fully utilize data migration mode or to re-protect data after a failure.

Imagine that you have a vSAN cluster with 16 hosts. There are four hosts per rack, therefore the hosts are divided over the four racks. Make a failure domain for each rack so that it is possible for the entire unit to fail. A cluster with this capacity may be configured by assigning the “Basic Level of Acceptable Failures” option to 1. Set up five failure domains in the cluster if you need the “Basic Level of Acceptable Failures” option to be set to 2.

All assets, namely CPU and rack memory, are inaccessible to the cluster when a rack fails. Configure more compact fault domains to lessen the effect of a probable rack failure. The total quantity of resources available in the cluster following a rack failure rises as the number of fault domains grows.

Follow these principles while working with fault domains:

Set up a minimum of three fault domains for the vSAN cluster. Configure 4 or more fault domains for the best results.
A node that is not a part of any fault domain is thought to be in a fault domain all on its own.
Each vSAN host does not need to be assigned to a failure domain. Consider making fault domains that are the same size if you employ fault domains to defend the vSAN environment.
vSAN nodes save their failure domain designations when switching to another cluster.
Set the same number of devices within every fault domain when constructing one.
The failure domain can contain any number of hosts. At a minimum, one host must be present in every failure domain.

Create a New Fault Domain in a vSAN Cluster

You can arrange hosts in various fault domains to make sure that virtual machine objects keep functioning normally even if a rack fails.

vSAN distributes protection elements, such as witnesses and clones of the virtual machine objects, across various fault domains when you deploy a VM on the cluster with fault domains. As a result, in addition to supporting a single host, hard disk, or https://joinilluminatiworldwide.com network failure, the vSAN system can now tolerate complete rack failures.

Navigate to the vSAN Cluster
Click the Settings tab
Under vSAN, click Fault Domains
Click the plus icon. The Create Fault Domain Wizard opens
Enter the name of the fault domain
Select one or more hosts to add to the fault domain
Click Create

The fault domain contains the chosen hosts. Information about the capacity that is consumed and reserved is displayed for each failure domain. You may see the capacity distribution in the fault domain by doing this.

Move host to selected fault domain

You can move a host to a chosen fault domain in a vSAN cluster.

Navigate to the vSAN Cluster
Click the Settings tab
Under vSAN, click Fault Domains
Click and drag the host you want to add to an existing fault domain

The selected host will appear in the fault domain

Move hosts out of the fault domain

You can relocate hosts away from a fault domain based on your needs.

But first, make sure the host is online because you cannot move offline or inaccessible hosts from the fault domain.

Navigate to the vSAN Cluster
Click the Settings tab
Under vSAN, click Fault Domains

The fault domain no longer includes the chosen host. Any host that isn’t included in a fault domain is said to be in a single-host fault domain.

Hosts can then be added to fault domains.

Fault domain rename

You can change the name of an existing fault domain in a vSAN cluster.

Navigate to the vSAN Cluster
Click the Settings tab
Under vSAN, click Fault Domains
Click “Apply” or “OK”

The new name will appear in the list of fault domains.

Remove selected fault domains

When you no longer need a fault domain, you can remove it from the vSAN cluster.

Navigate to the vSAN Cluster
Click the Settings tab
Under vSAN, click Fault Domains

All hosts in the fault domain are removed, and fbbcrew.com the selected fault domain is removed from the vSAN cluster. Each host not in a fault domain is believed to be in its own single-host fault domain.

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