I'm writing today to inquire about finding the exact point in the source where postgres writes to disk. I'm trying to implement some compression in postgres. The idea is to compress the data right when its written to disk, to reduce the amount of data written to disk, reducing the amount of time of disk read/write. I'm hoping that this reduction in disk IO latency is greater than the CPU cost incurred by compression, resulting in a speedup. I will be testing various compression libraries to see which (if any) work well for various query types. I've been looking through the source code, in src/backend/storage specifically. I'm thinking something in smgr is where i want to make my de/compress calls. Specifically in src/backend/storage/smgr/md.c in the functions mdwrite(...) and mdread(...). Am I in the right place? If not where should I look?