Non-volatile memory express (NVMe) over peripheral component interconnect express (PCIe) has been adopted in the storage system to provide low latency and high throughput. NVMe allows a host system to reduce latency because it offers a high parallel operation and optimized command processing flow. In addition, an introduction of emerging non-volatile memory (NVM) significantly reduces the solid state drive (SSD) latency. The latency reduction in the host system and SSD makes a relative ratio of PCIe fabric latency to total I/O latency considerably grow. Therefore, this paper proposes a novel I/O optimization method using the PCIe feature, virtual channel. Unlike conventional approaches with the same priority data path, based on SSD's internal latency, an emerging NVM-based NVMe SSD with the proposed architecture selects a prioritized virtual channel to provide deterministic I/O latency. Experimental results show that the proposed method with phase-change memory (PCM) SSD improves I/O determinism by processing 45 ~ 74% more commands within the predictable I/O latency than a conventional PCM SSD.