This section provides various general best practices for sizing your deployment.

• User density—If concurrency is a concern, calculate how many users will use the environment at the peak of utilization. For example, if only 80 percent are using the environment at any time, the environment must support only that number of users (plus a failure capacity).
• Disaster recovery—For DR planning, Dell Technologies recommends implementing a dual/multi-site solution. The goal is to keep the environment online and, in case of an outage, to perform an environment recovery with minimum disruption to the business.
• Management and compute clusters—For our small test environment, we used a combined management and compute cluster. For environments deployed at a larger scale, we recommend that you separate the management and compute layers. When creating a management cluster for a large-scale deployment, consider using the E-Series VxRail or the R640 platform to reduce the data center footprint. With a more easily configured platform, the V-Series VxRail or R740XD platforms are preferred for compute clusters.
• Network isolation—This design illustrates a two-NIC configuration per appliance with all the traffic separated logically using VLAN. When designing for larger-scale deployments, consider physically separating the management and VDI traffic from the vSAN traffic for traffic isolation and to improve network performance and scalability.
• FTT—Dell Technologies recommends sizing storage with NumberOfFailuresToTolerate (FTT) set to 1, which means that you must double the amount of total storage to accommodate the mirroring of each VMDK.
• Slack space—Dell Technologies also recommends adding an additional 30 percent of slack space to prevent automatic rebalancing of storage, which impacts performance. Automatic balancing occurs when the storage reaches 80 percent of the full threshold. Therefore, 70 percent is recommended to reserve a 10 percent buffer.
• All-Flash compared with hybrid:
  • Hybrid and all-flash configurations have similar performance results. Because hybrid uses spinning drives, consider the durability of the disks.
  • Only all-flash configurations offer deduplication and compression for vSAN. Dell Technologies recommends all-flash configurations for simplified data management.
  • All-flash configurations need considerably less storage capacity than hybrid configurations to produce similar FTT, as shown in the following table.

     Table 1.  FTT comparisons 

    VM size	FTM	FTT	Overhead	Configuration	Capacity required	Hosts required
    50 GB	RAID-1 (Mirrored)	1	2 x	Hybrid	100 GB	3
    50 GB	RAID-5 (3+1) (Erasure coding)	1	1.33 x	All-flash	66.5 GB	4
    50 GB	RAID-1 (Mirrored)	2	3 x	Hybrid	150 GB	4
    50 GB	RAID-6 (4+2)(Erasure coding)	2	1.5 x	All-flash	75 GB	6