In this article
Visible GPUs do not automatically pool VRAM; independent queues and splitting one graph are different operating strategies.
Multiple GPUs can support independent ComfyUI queues or parts of one workflow where the selected components support that placement. Two visible cards do not automatically pool VRAM or accelerate a single graph. Define whether the goal is more separate jobs or execution of a particular larger workflow.
Confirm visibility and actual assignment
ComfyUI’s startup reference describes visible CUDA devices and the default device. Visibility is only the first check. Determine which device the main model and each additional node actually use, then correlate the graph’s activity with per-device monitoring.
Preserve card identities rather than relying only on numbering that may change between environments. Record launch commands, workflow and node versions. A second card sitting idle is not proof of a fault if the configured graph never assigns work to it.
Compare distinct operating schemes
| Scheme | Goal | Main checks | Constraint |
|---|---|---|---|
| Independent instances | More separate jobs | Device and queue isolation | Shared CPU, RAM and disks |
| Split graph components | A specific workflow | Node support and data movement | No automatic common memory |
| One GPU with a queue | Simple sequential operation | Waiting time and capacity | Limited parallel execution |
These schemes need different acceptance tests. A larger aggregate output rate from independent workers does not establish that one image finishes faster. Likewise, a graph distributed for capacity may incur extra movement and require more operational preparation.
Start with independent control jobs
Run one known workflow on each intended worker and confirm its assigned device. Then submit the same representative set concurrently. Record completed outputs, errors, per-card memory and whole-job timing. Watch shared host resources because individually successful workers may compete for storage or RAM.
Keep input and output paths distinct or use a deliberate naming scheme. Separate processes should not silently overwrite one another’s results. Record queue ownership and how jobs are directed to a worker so the system can be reproduced after restart.
Test a distributed graph independently
Support for splitting a graph must be established for the actual components and versions. The modular structure and availability of custom nodes do not by themselves verify a proposed distribution method. Preserve the dependency and transfer path in the experiment record.
Compare complete output quality and time against the relevant control, not just whether both cards show activity. For hardware owners and operations funders, the conclusion should match the goal: aggregate jobs or one workflow’s capacity.
Official references: docs.comfy.org — startup flags, github.com — ComfyUI.
Related guides: ComfyUI offloading: when moving data to RAM helps, ComfyUI in the cloud: keeping models, workflows and outputs.