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Introduction

It is often desirable to add, remove or re-size storage devices while the operating system is running, and without rebooting. This manual outlines the procedures that may be used to reconfigure storage devices on Red Hat Enterprise Linux 5 host systems while the system is running. It covers iSCSI and Fibre Channel storage interconnects; other interconnect types may be added it the future.
The Online Storage Reconfiguration guide focuses on adding, removing, modifying, and monitoring storage devices. It does not discuss the Fibre Channel or iSCSI protocols in detail. For more information about these protocols, refer to other documentation.
This manual assumes that you have advanced working knowledge of Red Hat Enterprise Linux 5, along with first-hand experience in managing storage devices in Linux. Before consulting this book, verify if your host bus adapter vendor or hardware vendor have their own documentation. It is recommended that you consult such documents in conjunction with this manual.

Note

This manual makes reference to various sysfs objects. Red Hat advises that the sysfs object names and directory structure are subject to change in major Red Hat Enterprise Linux 5 releases. This is because the upstream Linux kernel does not provide a stable internal API. For guidelines on how to reference sysfs objects in a transportable way, refer to the document Documentation/sysfs-rules.txt in the kernel source tree for guidelines.

Warning

Online storage reconfiguration must be done carefully. System failures or interruptions during the process can lead to unexpected results. Red Hat advises that you reduce system load to the maximum extent possible during the change operations. This will reduce the chance of I/O errors, out-of-memory errors, or similar errors occurring in the midst of a configuration change. The following sections provide more specific guidelines regarding this.
In addition, Red Hat recommends that you back up all data before performing online storage reconfiguration.