Keepalived is a production-grade Linux daemon for high-availability and load balancing. It implements VRRP v2/v3 for router failover, integrates with the Linux Virtual Server (IPVS) kernel module for Layer 4 load balancing, and includes a suite of health checkers (HTTP, SSL, TCP, UDP, SMTP, DNS, PING, MISC) plus BFD for fast failure detection. The architecture is multi-process: a parent process manages dedicated children for VRRP, checkers, and BFD, coordinating reloads and termination via signals and eventfd. It deeply interacts with the Linux kernel through netlink, nftables/iptables, raw sockets, and proc connector, and exposes operational interfaces via SNMP, D-Bus, JSON state dumps, SMTP alerts, and notification scripts. The codebase is written in C with careful attention to Linux-specific features, including network namespaces, VRFs, VMAC/macvlan, and multicast group handling. It is a mature, widely deployed critical infrastructure component rather than a research artifact or library.
Open CAS Linux is a production-grade block-layer cache acceleration solution for Linux. It consists of a kernel module (`cas_cache`) implementing caching logic on top of the OCF (Open Cache Framework), a block device module (`cas_bd`), and a user-space management CLI (`casadm`). The system accelerates block I/O by caching hot data on fast storage (e.g., NVMe/Optane) while using slower backing storage, with support for multiple cache modes, cleaning policies, I/O classes, and statistics reporting. Management is performed via ioctls through `/dev/cas_ctrl` and netlink-based communication, with a comprehensive CLI (`casadm`) for cache/core lifecycle operations and statistics output in text, CSV, and raw CSV formats.