Red Hat CLUSTER SUITE FOR ENTERPRISE LINUX 5.1 Manual de usuario descargar pdf (Pagina 24)

Introduction to Linux Clustering

7.5 Clustered Filesystems

When using a block-level storage system like iSCSI, SAN, GNBD or DRBD a cluster

capable filesystem should be used, in order to allow multiple nodes to read and write at the

same time.

A clustered filesystem differs from a conventional filesystem by including features to handle

file-locking and journalling from multiple nodes.

7.5.1 CLVM

It is possible to run LVM on top of a centralised block storage device, by enabling clustered

locking in the LVM configuration and running the CLVM service together with CMAN for

clustering.

Once clustered LVM is enabled, it can be used in the exact same way as conventional LVM.

7.5.2 GFS – GLOBAL FILE SYSTEM

GFS is a clustered filesystem developed and supported by Redhat, and available on RHEL. It

is fully open source, and Redhat are currently working on getting it merged with the

mainstream kernel.

GFS has a number of powerful features that make it ideal for use in production clusters:

● Tried and tested technology, fully supported for customers of Redhat.

● Scales up to hundreds of cluster nodes.

● Supports extended access control lists.

● Supports user quotas.

● Dynamic symlinks (known as “Context Dependent Path Names”) which allow the

symlink to point to different locations depending on various variable of the node

using it. Ideal for node-dependent configuration.

7.5.3 EXT4 (UNDER DEVELOPMENT)

Most people are familiar with ext3 which is the default Linux filesystem for almost all

distributions.

In 2007 development started on ext4, which will fix the limitations of ext3. One of the new

features that is being developed with this release is support for clustered filesystems.

However, it is likely that ext4 will not be ready for production use for a number of years and

is only mentioned here for the reader's interest.

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Red Hat CLUSTER SUITE FOR ENTERPRISE LINUX 5.1 Manual de usuario Pagina 24