Disk Used - statvfs - system

What it does#

It reads the total amount of disk space used on the root filesystem by using the statvfs() system call. This provides system-wide disk usage information.

Classname#

• DiskUsedStatvfsSystemProvider

Metric Name#

• disk_used_statvfs_system

Input Parameters#

• args
  • -i: interval in milliseconds (optional, default: 1000 ms)

Example measuring system disk usage with an interval of 100 ms:

./metric-provider-binary -i 100

Output#

This metric provider prints to Stdout a continuous stream of data. The format of the data is as follows:

TIMESTAMP BYTES_USED

Where:

• TIMESTAMP: Unix timestamp, in microseconds
• BYTES_USED: The total amount of disk space used on the root filesystem, in bytes

Any errors are printed to Stderr.

How it works#

The provider uses the statvfs() system call to query filesystem statistics for the root filesystem (/).

The provider:

• calls statvfs("/", &buf) to get filesystem statistics
• calculates total space as f_blocks * f_frsize
• calculates free space as f_bfree * f_frsize
• returns used space as total_space - free_space

statvfs vs statfs#

This provider uses statvfs() which is the POSIX-compliant version of filesystem statistics, providing portable access to filesystem information across different Unix-like systems.

Free space calculation#

The provider uses f_bfree (free blocks available to superuser) rather than f_bavail (free blocks available to non-privileged users) to calculate free space. This means the “used” calculation includes space reserved for the superuser, providing a more accurate representation of actual disk utilization.

Root filesystem monitoring#

This provider specifically monitors the root filesystem (/) usage. In most systems, this represents the primary disk where the operating system and most applications are installed. If you have separate mount points for different filesystems, this provider will only report usage for the root filesystem.

The measurement represents the current total disk usage and is not cumulative - it’s an absolute measurement of how much disk space is currently occupied on the filesystem.