> instead of being exposed by OS as a seekable byte stream that can be appended/truncated on one end—is exposed by syscalls as a vector of fixed-sized extents

> instead of being exposed by OS as a seekable byte stream that can be appended/truncated on one end—is exposed by syscalls as a vector of fixed-sized extents That sounds similar to mainframe stuff like VSAM, where files are a stream of records instead of a stream of bytes.