GathervArrays does not support gathering... about adios2

[eisenhauer]

If I were guessing from your description it sounds like you are stressing BP5's ability to gather metadata. Some of the characteristics of BP5 that make it more efficient at scale, unfortunately put pressure on metadata size in the first timestep. BP5Writer takes steps to minimize this problem, but it can't be completely eliminated. That said, let me ask a quick question about your application. Are you writing attributes on all ranks? Or only on rank 0? (Attributes from all ranks are merged after being gathered, so writing duplicate attributes on non-zero ranks adds unnecessary pressure to metadata.).

[pgrete]

Thanks for the quick pointer! This fixed the issue.

For future reference (in case other people stumble across this):
We're using ADIOS2 through OpenPMD. Once I updated to current develop (from 0.15.2) there was an option available to specify the ranks that write attributes (adios2.attribute_writing_ranks = 0), which successfully solved the issue.