Procdiskstats

Procdiskstats is a virtual file in the Linux proc filesystem that exposes per‑block‑device input/output statistics. It is generated by the kernel’s block layer and is commonly used by system monitoring tools to analyze disk activity. Each line in the file corresponds to a single block device and is updated periodically as I/O activity occurs. The data in procdiskstats are intended as counters accumulated since boot, not real-time snapshots, so users typically sample the file over time to compute rates.

The format of procdiskstats is defined as three identifying fields followed by a series of counters. Each line begins with major and minor device numbers and the device name, then followed by 11 numeric counters: reads completed, reads merged, sectors read, ms reading, writes completed, writes merged, sectors written, ms writing, I/Os currently in progress, ms doing I/O, and weighted ms doing I/O. These fields describe aggregate I/O activity and latency measurements for each device and provide a compact view of disk performance without requiring specialized hardware probes.

Procdiskstats is widely used by monitoring tools such as iostat and other system statistics collectors. It complements other interfaces in the Linux I/O stack, including the sysfs and, on some systems, the newer per-device stat files under /sys. While the general structure has remained stable, the exact field set can vary with kernel version, so documentation for a given kernel release should be consulted for precise definitions.

Access to procdiskstats is generally read-only and provided by the kernel to userspace processes. It remains a common source for quick, low-overhead disk statistics in server and desktop environments. See also: /proc/diskstats, iostat, sysstat, Linux kernel documentation.