/proc/drbd

/proc/drbd is a virtual file provided by the DRBD kernel module on Linux systems. It serves as a real-time interface to display the status and health of DRBD (Distributed Replicated Block Device) devices used in high-availability and data replication scenarios.

Purpose

• Real-Time Monitoring: Provides up-to-date information on the state of DRBD devices, including roles (Primary/Secondary), connection status, synchronization progress, and disk state.

• Troubleshooting: Helps administrators diagnose issues related to replication, connectivity, and data consistency between nodes.

• Cluster Management: Allows operators to verify that DRBD devices are functioning as expected, supporting decision-making in high-availability clusters.

Key Information Displayed

When you view /proc/drbd (e.g., via cat /proc/drbd), you typically see details such as:

• Version Information: Displays the DRBD version and protocol details.

• Device Status: For each DRBD device, it shows:

  • Connection State: Indicates whether the nodes are connected.

  • Role Information: Specifies if the local node is Primary or Secondary.

  • Disk Status: Shows if the disk is UpToDate, Outdated, or Inconsistent.

  • Synchronization Data: Provides details about any ongoing synchronization (e.g., progress of data replication).

  • Metrics and Counters: Various counters related to network transfer and disk operations (e.g., number of sectors synchronized).

How to View /proc/drbd

You can view the DRBD status by running:

cat /proc/drbd

This command outputs a snapshot of the current state of all DRBD devices on the system.

Example Output

An example output might look like:

version: 8.4.10 (api:1/proto:86-104)
GIT-hash: 87c529c9d6785d85f8b2f45c26a5cf514e1c9f04 build by root@node on Tue Jul 28 14:01:24 UTC 2020
 0: cs:Connected ro:Primary/Secondary ds:UpToDate/D Unknown C r--
    ns:0 nr:0 dw:0 dr:0 al:0 bm:0 lo:0 pe:0 ua:0 ap:0 ep:0 wo:b oos:0

This indicates:

• Device 0 is active.

• The connection state is Connected.

• The local node is Primary and the remote node is Secondary.

• The data state shows UpToDate status.

• Additional counters provide insight into network and disk activity.

Conclusion

/proc/drbd is an essential tool for system administrators managing DRBD-based replication in high-availability environments. By inspecting this file, you can quickly assess the health and synchronization status of DRBD devices, making it easier to maintain data consistency and promptly address any replication issues.