I simply use SQLite for this. You can store the cache blocks in the SQLite database as blobs. One file, no sparse files. I don't think the "sparse file with separate metadata" approach is necessary here, and sparse files have hidden performance costs that grow with the number of populated extents. A sparse file is not all that different than a directory full of files. It might look like you're avoiding a filesystem lookup, but you're not; you've just moved it into the sparse extent lookup which you'll pay for every seek/read/write, not just once on open. You can simply use a regular file and let SQLite manage it entirely at the application level; this is no worse in performance and better for ops in a bunch of ways. Sparse files have a habit of becoming dense when they leave the filesystem they were created on.