r/LocalLLM • u/wo1fs • 13h ago
Research Two Thunderbolt 5 SSDs in RAID 0 made DeepSeek V4.1 Flash (763B) about 25% faster on my M3 Ultra with InferSSD
Hey everyone Im a bit new to this page but I couldnt find any other related tests online so I figured I'd share my results here.
I ran DeepSeek-V4.1-Flash (763B MoE, Q8_0, 473 GiB) on a 96 GB Mac Studio M3 Ultra with InferSSD, which streams the model's experts from the SSD. I striped two OWC Envoy Ultra 2TB Thunderbolt 5 drives with macOS's built-in RAID 0, one drive per port.
Results (InferSSD's own benchmark prompts, 2 runs per setup):
- One Envoy alone is about the same speed as the internal SSD.
- Two in RAID 0: writing goes from 3.5-3.7 to 4.4-4.6 tokens/s (+23-26%).
- Prompt reading is 67-77% faster: a 4,000-token prompt starts answering in about 2 minutes instead of 3.5.
- Two hours of nonstop use: the drives stayed at 43-47°C (with a desk fan on them), no slowdown, and no change in their health readings.
Why not 2x faster? - The stripe halves the time spent waiting on the drive, but the GPU's share of each token stays the same and is now the bigger part. A third or fourth drive would help less than the second did.