the 1TB/4TB seems to be the size of the included NVMe SSD.
the reserve now page also lists
NVIDIA DGX Spark Bundle
2 NVIDIA DGX Spark Units - 4TB with Connecting Cable $8,049
The DGX Spark specs lists an NVIDIA ConnectX-7 Smart NIC which is rated at 200Gbe to connect to another DGX Spark, for about double the amount of memory for models.
