I have two mining rigs running, one with 2GB GPUs and one with 8GB cards. Recently, the rig with the 2GB cards failed due to the inability to upload the DAG to the GPU.
What's the current DAG size for miners and when do we expect to hit GPU-relevant limits, e.g. 2GB, 3GB, 4GB and so on. Are there any precalculations available/possible?
The DAG started at 1 GB at the time of the Frontier launch, and increases by approximately 0.73x per year. That puts the current size at roughly 1.35 GB as of mid-January 2016 (feel free to comment with an exact link if anyone has one).
Following the same crude approximation:
However, it's likely that the switch to PoS will occur long before then.
For what it's worth, certain GPUs require the DAG to be uploaded in chunks. You should search on the forums with the name of your card to find if this solution has worked for other users running the same hardware.