When Virtual SAN is enabled in the manual mode for the host cluster, you can use a manual method of combing specific SSDs with specific HDDs and creating user-defined disk groups on a particular host.
This method contrasts with the semi-automatic claiming of disks for Virtual SAN, where you can select multiple disks to be consumed by Virtual SAN, but do not organize them into groups. Instead, after you select the disks, Virtual SAN creates default disk groups for you. In contrast, when you manually create a disk group, you can be more specific and organize selected disks into disk groups. You can select an SSD and HDD disks of your choice to form a disk group. The disk groups that you create belong to the particular host where the disks reside, and you cannot reassign the groups to another host.
When you create a disk group, your main consideration should be the ratio of SSD to HDD capacity. Although the ratios depend on use cases and workloads, the best practice is to use 1:10 ratio of the SSD to HDD capacity.
- Browse to the Virtual SAN cluster in the vSphere Web Client navigator.
- Click the Manage tab and click Settings.
- Under Virtual SAN, click Disk Management.
- Click the Create a new disk group icon.
- Select an SSD disk, and then select one or multiple non-SSD disks.
For each disk group, you can select only one SSD and up to six non-SSD disks.
- Click OK.
The new disk group appears on the list.