iSCSI Target must pass same block as the exported device ( RAID array is most cases).
If you use 4k disks, the RAID controller will also make 4k device and iSCSI Target must export it as 4k LUN.
As result, VMware will not accept such LUN.
For iSCSI you must use 512 disks, or NFS.
If you want to use 4k disks with NFS, you will need small update (contact our support) from us to enable 4k LUNs as they are disabled by default.
In such case both DSS nodes MUST have same disks. If first node has 512 and second 4k, the volume replication will NOT work properly and danger of destroying the data.