Chapter 13. Using OCFS2 with DRBD

This chapter outlines the steps necessary to set up a DRBD resource as a block device holding a shared Oracle Cluster File System, version 2 (OCFS2).


All cluster file systems require fencing - not only via the DRBD resource, but STONITH! A faulty member must be killed.

You’ll want these settings:

disk {
        fencing resource-and-stonith;
handlers {
        outdate-peer "/sbin/"

There must be no volatile caches! You might take a few hints of the page at, although that’s about GFS2, not OCFS2.

OCFS2 primer

The Oracle Cluster File System, version 2 (OCFS2) is a concurrent access shared storage file system developed by Oracle Corporation. Unlike its predecessor OCFS, which was specifically designed and only suitable for Oracle database payloads, OCFS2 is a general-purpose filesystem that implements most POSIX semantics. The most common use case for OCFS2 is arguably Oracle Real Application Cluster (RAC), but OCFS2 may also be used for load-balanced NFS clusters, for example.

Although originally designed for use with conventional shared storage devices, OCFS2 is equally well suited to be deployed on dual-Primary DRBD. Applications reading from the filesystem may benefit from reduced read latency due to the fact that DRBD reads from and writes to local storage, as opposed to the SAN devices OCFS2 otherwise normally runs on. In addition, DRBD adds redundancy to OCFS2 by adding an additional copy to every filesystem image, as opposed to just a single filesystem image that is merely shared.

Like other shared cluster file systems such as GFS, OCFS2 allows multiple nodes to access the same storage device, in read/write mode, simultaneously without risking data corruption. It does so by using a Distributed Lock Manager (DLM) which manages concurrent access from cluster nodes. The DLM itself uses a virtual file system (ocfs2_dlmfs) which is separate from the actual OCFS2 file systems present on the system.

OCFS2 may either use an intrinsic cluster communication layer to manage cluster membership and filesystem mount and unmount operation, or alternatively defer those tasks to the Pacemaker cluster infrastructure.

OCFS2 is available in SUSE Linux Enterprise Server (where it is the primarily supported shared cluster file system), CentOS, Debian GNU/Linux, and Ubuntu Server Edition. Oracle also provides packages for Red Hat Enterprise Linux (RHEL). This chapter assumes running OCFS2 on a SUSE Linux Enterprise Server system.