Use this list of requirements and recommendations for reference related to shared storage, vSAN principal storage, and NFS supplemental storage in an environment with a single or multiple VMware Cloud Foundation instances. The design also considers whether an instance contains a single or multiple availability zones.

After you set up the physical storage infrastructure, the configuration tasks for most design decisions are automated in VMware Cloud Foundation. You must perform the configuration manually only for a limited number of design elements as noted in the design implication.

For full design details, see vSAN Design for VMware Cloud Foundation.

Table 1. vSAN Design Requirements for VMware Cloud Foundation

Requirement ID

Design Requirement

Justification

Implication

VCF-VSAN-REQD-CFG-001

Provide sufficient raw capacity to meet the initial needs of the workload domain cluster.

Ensures that sufficient resources are present to create the workload domain cluster.

None.

VCF-VSAN-REQD-CFG-002
Provide at least the required minimum number of hosts according to the cluster type.

Satisfies the requirements for storage availability.

None.
Table 2. vSAN Design Requirements for Stretched Clusters with VMware Cloud Foundation

Requirement ID

Design Requirement

Justification

Implication

VCF-VSAN-REQD-CFG-003

Add the following setting to the default vSAN storage policy:

Site disaster tolerance = Site mirroring - stretched cluster

Provides the necessary protection for virtual machines in each availability zone, with the ability to recover from an availability zone outage.

You might need additional policies if third-party virtual machines are to be hosted in these clusters because their performance or availability requirements might differ from what the default VMware vSAN policy supports.

VCF-VSAN-REQD-CFG-004

Configure two fault domains, one for each availability zone. Assign each host to their respective availability zone fault domain.

Fault domains are mapped to availability zones to provide logical host separation and ensure a copy of vSAN data is always available even when an availability zone goes offline.

You must provide additional raw storage when the site mirroring - stretched cluster option is selected and fault domains are enabled.

VCF-VSAN-WTN-REQD-CFG-001

Deploy a vSAN witness appliance in a location that is not local to the ESXi hosts in any of the availability zones.

Ensures availability of vSAN witness components in the event of a failure of one of the availability zones.

You must provide a third physically-separate location that runs a vSphere environment. You might use a VMware Cloud Foundation instance in a separate physical location.

VCF-VSAN-WTN-REQD-CFG-002
Deploy a witness appliance of a size that corresponds to the required capacity of the cluster.

Ensures the witness appliance is sized to support the projected workload storage consumption.

The vSphere environment at the witness location must satisfy the resource requirements of the witness appliance.

VCF-VSAN-WTN-REQD-CFG-003

Connect the first VMkernel adapter of the vSAN witness appliance to the management network in the witness site.

Enables connecting the witness appliance to the workload domain vCenter Server.

The management networks in both availability zones must be routed to the management network in the witness site.

VCF-VSAN-WTN-REQD-CFG-004

Allocate a statically assigned IP address and host name to the management adapter of the vSAN witness appliance.

Simplifies maintenance and tracking, and implements a DNS configuration.

Requires precise IP address management.

VCF-VSAN-WTN-REQD-CFG-005

Configure forward and reverse DNS records for the vSAN witness appliance for the VMware Cloud Foundation instance.

Enables connecting the vSAN witness appliance to the workload domain vCenter Server by FQDN instead of IP address.

You must provide DNS records for the vSAN witness appliance.

VCF-VSAN-WTN-REQD-CFG-006

Configure time synchronization by using an internal NTP time for the vSAN witness appliance.

Prevents any failures in the stretched cluster configuration that are caused by time mismatch between the vSAN witness appliance and the ESXi hosts in both availability zones and workload domain vCenter Server.

  • An operational NTP service must be available in the environment.

  • All firewalls between the vSAN witness appliance and the NTP servers must allow NTP traffic on the required network ports.

VCF-VSAN-WTN-REQD-CFG-007

Configure an individual vSAN storage policy for each stretched cluster.

The vSAN storage policy of a stretched cluster cannot be shared with other clusters.

You must configure additional vSAN storage policies.
Table 3. vSAN Design Recommendations for VMware Cloud Foundation

Recommendation ID

Design Recommendation

Justification

Implication

VCF-VSAN-RCMD-CFG-001

Ensure that the storage I/O controller that is running the vSAN disk groups is capable and has a minimum queue depth of 256 set.

Storage controllers with lower queue depths can cause performance and stability problems when running vSAN.

vSAN ReadyNode servers are configured with the right queue depths for vSAN.

Limits the number of compatible I/O controllers that can be used for storage.

VCF-VSAN-RCMD-CFG-002

Do not use the storage I/O controllers that are running vSAN disk groups for another purpose.

Running non-vSAN disks, for example, VMFS, on a storage I/O controller that is running a vSAN disk group can impact vSAN performance.

If non-vSAN disks are required in ESXi hosts, you must have an additional storage I/O controller in the host.

VCF-VSAN-RCMD-CFG-003

Configure vSAN in all-flash configuration in the default workload domain cluster.

Meets the performance needs of the default workload domain cluster.

All vSAN disks must be flash disks, which might cost more than magnetic disks.

VCF-VSAN-RCMD-CFG-004

Provide sufficient raw capacity to meet the planned needs of the workload domain cluster.

Ensures that sufficient resources are present in the workload domain cluster, preventing the need to expand the vSAN datastore in the future.

None.

VCF-VSAN-RCMD-CFG-005

On the vSAN datastore, ensure that at least 30% of free space is always available.

This free space, called slack space, is set aside for host maintenance mode data evacuation, component rebuilds, rebalancing operations, and VM snapshots.

Increases the amount of available storage needed.

VCF-VSAN-RCMD-CFG-006

Configure vSAN with a minimum of two disk groups per ESXi host.

Reduces the size of the fault domain and spreads the I/O load over more disks for better performance.

Using multiple disk groups requires more disks in each ESXi host.

VCF-VSAN-RCMD-CFG-007

For the cache tier in each disk group, use a flash-based drive that is at least 600 GB large.

Provides enough cache for both hybrid or all-flash vSAN configurations to buffer I/O and ensure disk group performance.

Additional space in the cache tier does not increase performance.

Using larger flash disks can increase the initial host cost.

VCF-VSAN-RCMD-CFG-008

Use the default VMware vSAN storage policy.

  • Provides the level of redundancy that is needed in the workload domain cluster.

  • Provides the level of performance that is enough for the individual workloads.

You might need additional policies for third-party virtual machines hosted in these clusters because their performance or availability requirements might differ from what the default VMware vSAN policy supports.

VCF-VSAN-RCMD-CFG-009

Leave the default virtual machine swap file as a sparse object on vSAN.

Sparse virtual swap files consume capacity on vSAN only as they are accessed. As a result, you can reduce the consumption on the vSAN datastore if virtual machines do not experience memory over-commitment which would require the use of the virtual swap file.

None.

VCF-VSAN-RCMD-CFG-010

Use the existing vSphere Distributed Switch instance in the workload domain cluster.

Provides guaranteed performance for vSAN traffic in a connection-free network by using existing networking components. 

All traffic paths are shared over common uplinks.

VCF-VSAN-RCMD-CFG-011

Configure jumbo frames on the VLAN for vSAN traffic.

  • Simplifies configuration because jumbo frames are also used to improve the performance of vSphere vMotion and NFS storage traffic.

  • Reduces the CPU overhead resulting high network usage.

Every device in the network must support jumbo frames.
Table 4. vSAN Design Recommendations for Stretched Clusters with VMware Cloud Foundation

Recommendation ID

Design Recommendation

Justification

Implication

VCF-VSAN-WTN-RCMD-CFG-001

Configure the vSAN witness appliance to use the first VMkernel adapter, that is the management interface, for vSAN witness traffic.

Removes the requirement to have static routes on the witness appliance as witness traffic is routed over the management network.

The management networks in both availability zones must be routed to the management network in the witness site.

VCF-VSAN-WTN-RCMD-CFG-002

Place witness traffic on the management VMkernel adapter of all the ESXi hosts in the workload domain.

Separates the witness traffic from the vSAN data traffic. Witness traffic separation provides the following benefits:

  • Removes the requirement to have static routes from the vSAN networks in both availability zones to the witness site.

  • Removes the requirement to have jumbo frames enabled on the path between each availability zone and the witness site because witness traffic can use a regular MTU size of 1500 bytes.

The management networks in both availability zones must be routed to the management network in the witness site.