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esxi/vsan-claim-cache-count

Defines any additional command line options to pass to ansible for playbooks

This param defines how many Cache disks to claim from the available list of local disks on an ESXI host, after filtering out VSAN non-usable devices. By default only 1 (one) disk will be claimed as a Cache disk for the VSAN volumes. This param allows adjusting the selection list to add more Cache disks.

Note that the different claiming "rules" may choose to implement this differently.

In the "simple" disk claiming ruleset, all Boot disks, VSAN, and VMFS claimed disks are filtered out. The list of remaining disks are sorted by size; and then the first disk in the list is claimed for Cache disk.

Note that VSAN can only utilize 1 Cache and 7 Capacity disks as a maximum, per VSAN disk group. This Param is responsible for activating and building multiple VSAN disk groups. The number of Capacity disks in each VSAN disk group can be adjusted by using the Param esxi/vsan-claim-capacity-group-size.

In the "simple" claiming ruleset, setting this value to "2" (for example) will select the first 2 disks in the filtered list as Cache disks for the VSAND disk groups. Presumably these are smaller and faster disk types.

With 2 Cache disks specified, there will be at most 2 VSAN disk groups created, as long as there are 8 or more disks (assuming the disk group size default of 7 is used). The code will claim the first 7 disks for the first VSAN disk group, then the remainder up to 7 for the second VSAN disk group. Any remaining capacity disks will not be used.

If there are 17 capacity disks, setting this Param to 3 will result in the following disk groups being built (again, assuming disk group size is default of 7):

  • group 1 will have 1 cache and 7 capacity disks
  • group 2 will have 1 cache and 7 capacity disks
  • group 3 will have 1 cache and 3 capacity disks

The 7 disks capacity limit is a VMware restriction.

In addition - there can be no more than 5 VSAN disk groups which means that a single VSAN host can only support a maximum of 35 Capacity disks, which would require 5 Cache disks for a total of 40 VSAN claimed disks.

Note

This Param will NOT effect VSAN Witness VM disk claiming Cache disk count. That must be hard coded to only 1 Cache disk, as such, this Param is ignored during VSAN Witness disk claiming process.