When attempting to create a vSAN disk group or add a disk to an existing group, the vSAN device appears as 'Ineligible for use by vSAN' in vSphere Client > vSAN Cluster > Configure > Disk Management > Host > Ineligible and Unclaimed:
VMware vSAN 7.x
VMware vSAN 8.x
For a disk to be eligible for use in vSAN, it must not have any partitions on it. If any partitions exist on the disk, especially remains from previous configurations, vSAN will mark the disk as ineligible for use.
Navigate to affected ESXi host > Configure > Storage Devices. Selected the affected LUN and click on Partition details to display the partitions.
vdq -qHDiskResult[11]:Name: ######################################VSANUUID:State: Ineligible for use by VSANReason: Has partitionsStoragePoolState: Ineligible for use by Storage PoolStoragePoolReason: Has partitionsIsSSD?: 1IsCapacityFlash?: 0IsPDL ?: 0Size(MB): 3662830FormatType: 512eIsVsanDirectDisk?: 0
Certain functionalities, such as vSAN or virtual flash resource, require that your ESXi host uses clean storage devices. You can erase an HHD or flash device and remove all existing data.
Make sure that the host is in the connected state.
Verify that the devices you plan to erase are not in use or used at ESXi core storage level.
Required privilege: Host.Config.Storage
Refer : Erase ESXi Storage Devices
If the above steps do not work the follow the fix mentioned in Cannot claim New Capacity Disks to be part of vSAN Disk Group
If the above also does not work, then clear the partitions on the device from the hardware management console (iLO, iDRAC, and so on).