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documentation.suse.com / SUSE Linux Enterprise High Availability Documentation / Administration Guide / Storage and Data Replication / OCFS2
Applies to SUSE Linux Enterprise High Availability 12 SP5

16 OCFS2

  

Oracle Cluster File System 2 (OCFS2) is a general-purpose journaling file system that has been fully integrated since the Linux 2.6 Kernel. OCFS2 allows you to store application binary files, data files, and databases on devices on shared storage. All nodes in a cluster have concurrent read and write access to the file system. A user space control daemon, managed via a clone resource, provides the integration with the HA stack, in particular with Corosync and the Distributed Lock Manager (DLM).

16.1 Features and Benefits

  

OCFS2 can be used for the following storage solutions for example:

  • General applications and workloads.

  • Xen image store in a cluster. Xen virtual machines and virtual servers can be stored on OCFS2 volumes that are mounted by cluster servers. This provides quick and easy portability of Xen virtual machines between servers.

  • LAMP (Linux, Apache, MySQL, and PHP | Perl | Python) stacks.

As a high-performance, symmetric and parallel cluster file system, OCFS2 supports the following functions:

  • An application's files are available to all nodes in the cluster. Users simply install it once on an OCFS2 volume in the cluster.

  • All nodes can concurrently read and write directly to storage via the standard file system interface, enabling easy management of applications that run across the cluster.

  • File access is coordinated through DLM. DLM control is good for most cases, but an application's design might limit scalability if it contends with the DLM to coordinate file access.

  • Storage backup functionality is available on all back-end storage. An image of the shared application files can be easily created, which can help provide effective disaster recovery.

OCFS2 also provides the following capabilities:

  • Metadata caching.

  • Metadata journaling.

  • Cross-node file data consistency.

  • Support for multiple-block sizes up to 4 KB, cluster sizes up to 1 MB, for a maximum volume size of 4 PB (Petabyte).

  • Support for up to 32 cluster nodes.

  • Asynchronous and direct I/O support for database files for improved database performance.

Note
Note: Support for OCFS2

OCFS2 is only supported by SUSE when used with the pcmk (Pacemaker) stack, as provided by SUSE Linux Enterprise High Availability. SUSE does not provide support for OCFS2 in combination with the o2cb stack.

16.2 OCFS2 Packages and Management Utilities

  

The OCFS2 Kernel module (ocfs2) is installed automatically in SUSE Linux Enterprise High Availability 12 SP5. To use OCFS2, make sure the following packages are installed on each node in the cluster: ocfs2-tools and the matching ocfs2-kmp-* packages for your Kernel.

The ocfs2-tools package provides the following utilities for management of OFS2 volumes. For syntax information, see their man pages.

Table 16.1: OCFS2 Utilities
  

OCFS2 Utility

Description

debugfs.ocfs2

Examines the state of the OCFS file system for debugging.

fsck.ocfs2

Checks the file system for errors and optionally repairs errors.

mkfs.ocfs2

Creates an OCFS2 file system on a device, usually a partition on a shared physical or logical disk.

mounted.ocfs2

Detects and lists all OCFS2 volumes on a clustered system. Detects and lists all nodes on the system that have mounted an OCFS2 device or lists all OCFS2 devices.

tunefs.ocfs2

Changes OCFS2 file system parameters, including the volume label, number of node slots, journal size for all node slots, and volume size.

16.3 Configuring OCFS2 Services and a STONITH Resource

  

Before you can create OCFS2 volumes, you must configure the following resources as services in the cluster: DLM and a STONITH resource.

The following procedure uses the crm shell to configure the cluster resources. Alternatively, you can also use Hawk2 to configure the resources as described in Section 16.6, “Configuring OCFS2 Resources With Hawk2”.

Procedure 16.1: Configuring a STONITH Resource
  
Note
Note: STONITH Device Needed

You need to configure a fencing device. Without a STONITH mechanism (like external/sbd) in place the configuration will fail.

  1. Start a shell and log in as root or equivalent.

  2. Create an SBD partition as described in Procedure 10.3, “Initializing the SBD Devices”.

  3. Run crm configure.

  4. Configure external/sbd as the fencing device: 

    crm(live)configure# primitive sbd_stonith stonith:external/sbd \
  params pcmk_delay_max=30 meta target-role="Started"

  5. Review your changes with show.

  6. If everything is correct, submit your changes with commit and leave the crm live configuration with exit.

For details on configuring the resource group for DLM, see Procedure 15.1, “Configuring a Base Group for DLM”.

16.4 Creating OCFS2 Volumes

  

After you have configured a DLM cluster resource as described in Section 16.3, “Configuring OCFS2 Services and a STONITH Resource”, configure your system to use OCFS2 and create OCFs2 volumes.

Note
Note: OCFS2 Volumes for Application and Data Files

We recommend that you generally store application files and data files on different OCFS2 volumes. If your application volumes and data volumes have different requirements for mounting, it is mandatory to store them on different volumes.

Before you begin, prepare the block devices you plan to use for your OCFS2 volumes. Leave the devices as free space.

Then create and format the OCFS2 volume with the mkfs.ocfs2 as described in Procedure 16.2, “Creating and Formatting an OCFS2 Volume”. The most important parameters for the command are listed in Table 16.2, “Important OCFS2 Parameters”. For more information and the command syntax, refer to the mkfs.ocfs2 man page.

Table 16.2: Important OCFS2 Parameters
  

OCFS2 Parameter

Description and Recommendation

Volume Label (-L)

A descriptive name for the volume to make it uniquely identifiable when it is mounted on different nodes. Use the tunefs.ocfs2 utility to modify the label as needed.

Cluster Size (-C)

Cluster size is the smallest unit of space allocated to a file to hold the data. For the available options and recommendations, refer to the mkfs.ocfs2 man page.

Number of Node Slots (-N)

The maximum number of nodes that can concurrently mount a volume. For each of the nodes, OCFS2 creates separate system files, such as the journals. Nodes that access the volume can be a combination of little-endian architectures (such as AMD64/Intel 64) and big-endian architectures (such as IBM Z).

Node-specific files are called local files. A node slot number is appended to the local file. For example: journal:0000 belongs to whatever node is assigned to slot number 0.

Set each volume's maximum number of node slots when you create it, according to how many nodes that you expect to concurrently mount the volume. Use the tunefs.ocfs2 utility to increase the number of node slots as needed. Note that the value cannot be decreased, and one node slot will consume about 100 MiB disk space.

In case the -N parameter is not specified, the number of node slots is decided based on the size of the file system. For the default value, refer to the mkfs.ocfs2 man page.

Block Size (-b)

The smallest unit of space addressable by the file system. Specify the block size when you create the volume. For the available options and recommendations, refer to the mkfs.ocfs2 man page.

Specific Features On/Off (--fs-features)

A comma separated list of feature flags can be provided, and mkfs.ocfs2 will try to create the file system with those features set according to the list. To turn a feature on, include it in the list. To turn a feature off, prepend no to the name.

For an overview of all available flags, refer to the mkfs.ocfs2 man page.

Pre-Defined Features (--fs-feature-level)

Allows you to choose from a set of pre-determined file system features. For the available options, refer to the mkfs.ocfs2 man page.

If you do not specify any features when creating and formatting the volume with mkfs.ocfs2, the following features are enabled by default: backup-super, sparse, inline-data, unwritten, metaecc, indexed-dirs, and xattr.

Procedure 16.2: Creating and Formatting an OCFS2 Volume
  

Execute the following steps only on one of the cluster nodes.

  1. Open a terminal window and log in as root.

  2. Check if the cluster is online with the command crm status.

  3. Create and format the volume using the mkfs.ocfs2 utility. For information about the syntax for this command, refer to the mkfs.ocfs2 man page.

    For example, to create a new OCFS2 file system that supports up to 32 cluster nodes, enter the following commands: 

    #  mkfs.ocfs2 -N 32 /dev/disk/by-id/DEVICE_ID

16.5 Mounting OCFS2 Volumes

  

You can either mount an OCFS2 volume manually or with the cluster manager, as described in Procedure 16.4, “Mounting an OCFS2 Volume with the Cluster Resource Manager”.

Procedure 16.3: Manually Mounting an OCFS2 Volume
  

  1. Open a terminal window and log in as root.

  2. Check if the cluster is online with the command crm status.

  3. Mount the volume from the command line, using the mount command.

Warning
Warning: Manually Mounted OCFS2 Devices

If you mount the OCFS2 file system manually for testing purposes, make sure to unmount it again before starting to use it by means of cluster resources.

Procedure 16.4: Mounting an OCFS2 Volume with the Cluster Resource Manager
  

To mount an OCFS2 volume with the High Availability software, configure an ocfs2 file system resource in the cluster. The following procedure uses the crm shell to configure the cluster resources. Alternatively, you can also use Hawk2 to configure the resources as described in Section 16.6, “Configuring OCFS2 Resources With Hawk2”.

  1. Start a shell and log in as root or equivalent.

  2. Run crm configure.

  3. Configure Pacemaker to mount the OCFS2 file system on every node in the cluster: 

    crm(live)configure# primitive ocfs2-1 ocf:heartbeat:Filesystem \
  params device="/dev/disk/by-id/DEVICE_ID" directory="/mnt/shared" \
  fstype="ocfs2" options="acl" \
  op monitor interval="20" timeout="40" \
  op start timeout="60" op stop timeout="60" \
  meta target-role="Stopped"

  4. Add the ocfs2-1 primitive to the g-storage group you created in Procedure 15.1, “Configuring a Base Group for DLM”. 

    crm(live)configure# modgroup g-storage add ocfs2-1

    The add subcommand appends the new group member by default. Because of the base group's internal colocation and ordering, Pacemaker will only start the ocfs2-1 resource on nodes that also have a dlm resource already running.

  5. Review your changes with show.

  6. If everything is correct, submit your changes with commit and leave the crm live configuration with exit.

16.6 Configuring OCFS2 Resources With Hawk2

  

Instead of configuring the DLM and the file system resource for OCFS2 manually with the crm shell, you can also use the OCFS2 template in Hawk2's Setup Wizard.

Important
Important: Differences Between Manual Configuration and Hawk2

The OCFS2 template in the Setup Wizard does not include the configuration of a STONITH resource. If you use the wizard, you still need to create an SBD partition on the shared storage and configure a STONITH resource as described in Procedure 16.1, “Configuring a STONITH Resource”.

Using the OCFS2 template in the Hawk2 Setup Wizard also leads to a slightly different resource configuration than the manual configuration described in Procedure 15.1, “Configuring a Base Group for DLM” and Procedure 16.4, “Mounting an OCFS2 Volume with the Cluster Resource Manager”.

Procedure 16.5: Configuring OCFS2 Resources with Hawk2's Wizard
  

  1. Log in to Hawk2: 

    https://HAWKSERVER:7630/

  2. In the left navigation bar, select Wizard.

  3. Expand the File System category and select OCFS2 File System.

  4. Follow the instructions on the screen. If you need information about an option, click it to display a short help text in Hawk2. After the last configuration step, Verify the values you have entered.

    The wizard displays the configuration snippet that will be applied to the CIB and any additional changes, if required.

    Image

  5. Check the proposed changes. If everything is according to your wishes, apply the changes.

    A message on the screen shows if the action has been successful.

16.7 Using Quotas on OCFS2 File Systems

  

To use quotas on an OCFS2 file system, create and mount the files system with the appropriate quota features or mount options, respectively: ursquota (quota for individual users) or grpquota (quota for groups). These features can also be enabled later on an unmounted file system using tunefs.ocfs2.

When a file system has the appropriate quota feature enabled, it tracks in its metadata how much space and files each user (or group) uses. Since OCFS2 treats quota information as file system-internal metadata, you do not need to run the quotacheck(8) program. All functionality is built into fsck.ocfs2 and the file system driver itself.

To enable enforcement of limits imposed on each user or group, run quotaon(8) like you would do for any other file system.

For performance reasons each cluster node performs quota accounting locally and synchronizes this information with a common central storage once per 10 seconds. This interval is tuneable with tunefs.ocfs2, options usrquota-sync-interval and grpquota-sync-interval. Therefore quota information may not be exact at all times and as a consequence users or groups can slightly exceed their quota limit when operating on several cluster nodes in parallel.

16.8 For More Information

  

For more information about OCFS2, see the following links:

https://ocfs2.wiki.kernel.org/

The OCFS2 project home page.

http://oss.oracle.com/projects/ocfs2/

The former OCFS2 project home page at Oracle.

http://oss.oracle.com/projects/ocfs2/documentation

The project's former documentation home page.