Chapter 1

Atomic rename, unlink with open file descriptors, O_TMPFILE, file locking (flock vs fcntl), and sparse files. POSIX operations that reliable software depends on.

Understanding buffered IO, direct IO (O_DIRECT), synchronous IO flags (O_SYNC, fsync), and how different filesystems handle these modes.

How the page cache works, read-ahead mechanisms, dirty page writeback, and memory reclaim. Essential for understanding Linux filesystem performance.

How mmap() works, its relationship to the page cache, when writes actually reach disk, and mmap coherence across local and network filesystems.

End-to-end checksumming, copy-on-write architecture, integrated RAID, and snapshots. Understand ZFS's unique features, RAM requirements, and when to choose it over traditional filesystems.

What recordsize controls, compression interaction, workload matching, performance measurement, and code walkthrough.

Coordinating concurrent access across processes on one host. POSIX semantics, advisory and mandatory locking, and what the kernel does and does not serialize for you.

Surviving crashes, power loss, and corruption. Journaling, copy-on-write, fsync semantics, and checksumming.

Block allocation, metadata overhead, caching strategies, and IO patterns on local storage.

Battle-tested techniques: squashfs on NFS, tmpfs for performance testing, loop devices, bind mounts, sparse files, and FUSE. Unconventional approaches that solve real problems.

Device and pool statistics with iostat, blktrace, and zpool iostat, plus eBPF/bpftrace scenarios. Telling a slow device from a stalled writeback from an application waiting on its own fsync.