I want to create a RAID 6 using 4 HDD 1.5TB using the S/W RAID feature Open-E offer. But the software says I'm exceeding the limit, as I'm using 4TB license key.

I created the S/W RAID using the demo and got array of size (2.7TB) then use the module again, but the message is still prompting, even though the array is smaller than 4TB.

The storage limit is based on disks that are seen by "fdisk -l". If it is SW RAID then the system sees all disks and adds up overall capacity. In H/W RAID it is different as RAID controller reports to the system capacity of created RAID units, not all single disks.