Spot Capacity Arbitrage & Preemption Resilience
Cloud spot (preemptible) GPU instances are priced at 60%–75% discounts compared to on-demand instances. However, cloud providers can reclaim spot instances with only 30 to 120 seconds notice. Building a preemption-resilient training framework unlocks millions of dollars in compute savings.
Preemption Notice Window
When AWS/GCP/Azure issues a spot termination notice (via cloud metadata API), the training orchestrator has 30–120 seconds to snapshot local optimizer states, flush rank buffers, and exit gracefully.
Fast Local-Flash State Dumping
Writing a 100GB checkpoint directly to cloud S3 over the WAN takes minutes and fails the spot deadline. Fast local NVMe streaming dumps state in < 15 seconds, followed by out-of-band upload.
Dynamic Elastic Resharding
If a 64-node cluster loses 8 nodes to spot preemption, elastic frameworks (such as TorchElastic / Oobleck) reshard model and data parallel ranks across the remaining 56 nodes within 60 seconds without human intervention.
If spot discount is 65% (Rate_spot = 0.35 * Rate_on-demand) and preemption interruptions add 5% overhead in rework time (T_rework = 0.05 * T_run), total cost is 0.35 * 1.05 = 36.75% of on-demand cost—achieving net 63.25% dollar savings.
- Poll cloud metadata endpoints (e.g., http://169.254.169.254/latest/meta-data/spot/instance-action) every 2 seconds from a background daemon.
- Distribute spot allocations across multiple cloud availability zones and GPU instance families to minimize correlated multi-node preemption events.
- Maintain a hybrid cluster strategy: anchor critical pipeline parallel stages on reserved nodes while running data-parallel workers on spot capacity.