It depends on whether you're talking about 100 GB repository size or working copy size.
- Currently no partial/shallow clones, so you need to materialize the entire repo on disk.
- Working copy status can take a while (see https://github.com/martinvonz/jj/issues/1841 for tracking issue). This can be ameliorated at present by configuring Watchman as a filesystem monitor, and work is underway to improve status further.
- No support for Git LFS at present (even in colocated repos). When using the Git backend with jj, you would expect the same problems with regards to large file management.
- I haven't noticed any particular performance issues when interacting with the object store a large repository. It should be approximately the same as for Git since it uses libgit2 for the Git backend.
- Faster for operations that can be done in-memory in jj but only on-disk with Git, such as various rebase operations.
