vSAN Design for VMware Cloud Foundation

VMware Cloud Foundation uses VMware vSAN as the principal storage type for the management domain and recommended for use as principal storage in VI workload domains. You must determine the size of the compute and storage resources for the vSAN storage, and the configuration of the network carrying vSAN traffic. For multiple availability zones, you extend the resource size and determine the configuration of the vSAN witness host.

Logical Design for vSAN for VMware Cloud Foundation

vSAN is a cost-efficient storage technology that provides a simple storage management user experience, and permits a fully automated initial deployment of VMware Cloud Foundation. It also provides support for future storage expansion and implementation of vSAN stretched clusters in a workload domain.

Virtual machines on vSphere clusters consume a vSAN principal datastore that uses flash, NVMe or SATA disk drives. The vSphere cluster might also be connected to an optional supplemental datastore. — Figure 1. vSAN Logical Design for VMware Cloud Foundation

Table 1. vSAN Logical Design
Workload Domain Type	VMware Cloud Foundation Instances with a Single Availability Zone	VMware Cloud FoundationInstances with Multiple Availability Zones
Management domain (default cluster)	Four nodes minimum	Must be stretched first 8 node minimum, equally distributed across availability zones vSAN witness appliance in a third fault domain
Management domain (additional clusters)	Three nodes minimum Four nodes minimum is recommended for higher availability	Six nodes minimum, equally distributed across availability zones Eight nodes minimum is recommended for higher availability vSAN witness appliance in a third fault domain
VI workload domain (all clusters)	Three nodes minimum Four nodes minimum is recommended for higher availability	Six nodes minimum, equally distributed across availability zones Eight nodes minimum is recommended for higher availability vSAN witness appliance in a third fault domain

Hardware Configuration for vSAN for VMware Cloud Foundation

Determine the type of the capacity and caching devices, and the storage controllers for performance and stability according to the requirements of the management components of VMware Cloud Foundation.

vSAN Physical Requirements and Dependencies

vSAN has the following requirements and options:

vSAN Original Storage Architecture (OSA) as hybrid storage or all-flash storage.
- A vSAN hybrid storage configuration requires both magnetic devices and flash caching devices. The cache tier must be at least 10% of the size of the capacity tier.
- An all-flash vSAN configuration requires flash devices for both the caching and capacity tiers.
- VMware vSAN ReadyNodes or hardware from the VMware Compatibility Guide to build your own.
vSAN Express Storage Architecture (ESA)
- All storage devices claimed by vSAN contribute to capacity and performance. Each host's storage devices claimed by vSAN form a storage pool. The storage pool represents the amount of caching and capacity provided by the host to the vSAN datastore.
- ESXi hosts must be on the vSAN ESA Ready Node HCL with a minimum of 512 GB RAM per host.
Note: vSAN Express Storage Architecture is not supported with VMware Cloud Foundation.

For best practices, capacity considerations, and general recommendations about designing and sizing a vSAN cluster, see the VMware vSAN Design and Sizing Guide.

Network Design for vSAN for VMware Cloud Foundation

In the network design for vSAN in VMware Cloud Foundation, you determine the network configuration for vSAN traffic.

Consider the overall traffic bandwidth and decide how to isolate storage traffic.

Consider how much vSAN data traffic is running between ESXi hosts.
The amount of storage traffic depends on the number of VMs that are running in the cluster, and on how write-intensive the I/O process is for the applications running in the VMs.

For information on the physical network setup for vSAN traffic, and other system traffic, see Physical Network Infrastructure Design for VMware Cloud Foundation.

For information on the virtual network setup for vSAN traffic, and other system traffic, see Logical vSphere Networking Design for VMware Cloud Foundation.

The vSAN network design includes these components.

Table 2. Components of vSAN Network Design
Design Component	Description
Physical NIC speed	For best and most predictable performance (IOPS) for the environment, this design uses a minimum of a 10-GbE connection, with 25-GbE recommended, for use with vSAN all-flash configurations.
VMkernel network adapters for vSAN	The vSAN VMkernel network adapter on each ESXi host is created when you enable vSAN on the cluster. Connect the vSAN VMkernel network adapters on all ESXi hosts in a cluster to a dedicated distributed port group including also ESXi hosts that are not contributing storage resources to the cluster.
VLAN	All storage traffic should be isolated on its own VLAN. When a design uses multiple vSAN clusters, each cluster should use a dedicated VLAN or segment for its traffic. This approach increases security, prevents interference between clusters, and helps with troubleshooting cluster configuration.
Jumbo frames	vSAN traffic can be handled by using jumbo frames. Use jumbo frames for vSAN traffic only if the physical environment is already configured to support them, they are part of the existing design, or if the underlying configuration does not create a significant amount of added complexity to the design.

vSAN Witness Design for VMware Cloud Foundation

The vSAN witness appliance is a specialized ESXi installation that provides quorum and tiebreaker services for stretched clusters in VMware Cloud Foundation.

vSAN Witness Deployment Specification

When using vSAN in a stretched cluster configuration, you must deploy a witness ESXi host. This appliance must be deployed in a third location that is not local to the ESXi hosts on either side of the stretched cluster.

Table 3. vSAN Witness Appliance Sizing Considerations
Appliance Size	Maximum Number of Supported Virtual Machines	Maximum Number of Supported Witness Components
Tiny	10	750
Medium	500	21, 000
Large	500	64, 000

vSAN Witness Network Design

When using two availability zones, connect the vSAN witness appliance to the workload domain vCenter Server so that you can perform the initial setup of the stretched cluster and have workloads failover between the zones.

VMware Cloud Foundation uses vSAN witness traffic separation where you can use a VMkernel adapter for vSAN witness traffic that is different from the adapter for vSAN data traffic. In this design, you configure vSAN witness traffic in the following way:

On each ESXi host in both availability zones, place the vSAN witness traffic on the management VMkernel adapter.
On the vSAN witness appliance, use the same VMkernel adapter for both management and witness traffic.

For information about vSAN witness traffic separation, see vSAN Stretched Cluster Guide on VMware Cloud Platform Tech Zone.

Management network

Routed to the management networks in both availability zones. Connect the first VMkernel adapter of the vSAN witness appliance to this network. The second VMkernel adapter on the vSAN witness appliance is not used.

Place the following traffic on this network:

Management traffic
vSAN witness traffic

he witness appliance is connected to the management network in the third location for management and witness traffic. The management network is routed to the management networks in the two availability zones of the management and VI workload domains. — Figure 2. vSAN Witness Network Design

vSAN Design Requirements and Recommendations for VMware Cloud Foundation

Consider the requirements for using vSAN storage for standard and stretched clusters in VMware Cloud Foundation, such as required capacity, number of hosts, number of disk groups, storage policy, and the similar best practices for having vSAN operate in an optimal way.

For related vSphere cluster requirements and recommendations, see vSphere Cluster Design Requirements and Recommendations for VMware Cloud Foundation.

vSAN Design Requirements

You must meet the following design requirements for standard and stretched clusters in your vSAN design for VMware Cloud Foundation.

Table 4. 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 5. 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.

vSAN Design Recommendations

In your vSAN design for VMware Cloud Foundation, you can apply certain best practices for standard and stretched clusters .

Table 6. 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 7. 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.