Plan the configuration of the hosts in the Virtual SAN cluster for best performance and availability.
Memory and CPU
Size the memory and the CPU of the hosts in the Virtual SAN cluster based on the following considerations.
Hosts that have less than 512 GB memory can boot from a USB, SD, or SATADOM device. If the memory of the host is greater than 512 GB, boot the host from a SATADOM or disk device.
Provide more bandwidth for Virtual SAN traffic to improve performance.
- If you plan to use hosts that have 1-GbE adapters, dedicate adapters for Virtual SAN only. For all-flash configurations, plan hosts that have dedicated or shared 10-GbE adapters.
- If you plan to use 10-GbE adapters, they can be shared with other traffic types for both hybrid and all-flash configurations.
- If a 10-GbE adapter is shared with other traffic types, use a vSphere Distributed Switch for Virtual SAN traffic to isolate the traffic by using Network I/O Control and VLANs.
- Create a team of physical adapters for Virtual SAN traffic for redundancy.
Multiple Disk Groups
An entire disk group can fail if the flash cache or storage controller stops responding. As a result, Virtual SAN rebuilds all components for the failed disk group from another location in the cluster.
Use of multiple disk groups, with each disk group providing less capacity, provides the following benefits and disadvantages:
- Performance is improved because the datastore has more aggregated cache, and I/O operations are faster.
- Risk of failure is spread among multiple disk groups, and performance is improved in the case of disk group failure because Virtual SAN rebuilds fewer components
- Costs are increased because two or more caching devices are required.
- More memory is required to handle more disk groups.
- Multiple storage controllers are required to reduce the risk of a single point of failure.
For easy maintenance, consider hosts whose drive bays and PCIe slots are located at the front of the server body.
Blade Servers and External Storage
The capacity of blade servers usually does not scale in a Virtual SAN datastore because they have a limited number of disk slots. To extend the planned capacity of blade servers, use external storage enclosures. For information about the supported models of external storage enclosures, see VMware Compatibility Guide.
Hot Plug and Swap of Devices
Consider the storage controller passthrough mode support for easy hot plugging or replacement of magnetic disks and flash capacity devices on a host. If a controller works in RAID 0 mode, you must perform additional steps before the host can discover the new drive.