User manual REDHAT GNBD WITH GLOBAL FILE SYSTEM 5.2 CONFIGURATION

[. . . ] Software Versions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Related Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Feedback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Document Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] In order of how critical the information is to you, these items are marked as follows: Note A note is typically information that you need to understand the behavior of the system. Tip A tip is typically an alternative way of performing a task. Important Important information is necessary, but possibly unexpected, such as a configuration change that will not persist after a reboot. ix Introduction Caution A caution indicates an act that would violate your support agreement, such as recompiling the kernel. Warning A warning indicates potential data loss, as may happen when tuning hardware for maximum performance. x Chapter 1. Using GNBD with Red Hat GFS GNBD (Global Network Block Device) provides block-level storage access over an Ethernet LAN. GNBD components run as a client in a GFS node and as a server in a GNBD server node. A GNBD server node exports block-level storage from its local storage (either directly attached storage or SAN storage) to a GFS node. Table 1. 1, "GNBD Software Subsystem Components" summarizes the GNBD software subsystems components. Software Subsystem GNBD Components gnbd. ko Description Kernel module that implements the GNBD device driver on clients. Command to create, export and manage GNBDs on a GNBD server. Command to import and manage GNBDs on a GNBD client. A server daemon that allows a node to export local storage over the network. gnbd_export gnbd_import gnbd_serv Table 1. 1. GNBD Software Subsystem Components You can configure GNBD servers to work with device-mapper multipath. GNBD with device-mapper multipath allows you to configure multiple GNBD server nodes to provide redundant paths to the storage devices. The GNBD servers, in turn, present multiple storage paths to GFS nodes via redundant GNBDs. When using GNBD with device-mapper multipath, if a GNBD server node becomes unavailable, another GNBD server node can provide GFS nodes with access to storage devices. This document how to use GNBD with Red Hat GFS and consists of the following chapters: · Chapter 2, Considerations for Using GNBD with Device-Mapper Multipath · Chapter 3, GNBD Driver and Command Usage · Chapter 4, Running GFS on a GNBD Server Node 1 2 Chapter 2. Considerations for Using GNBD with Device-Mapper Multipath GNBD with device-mapper multipath allows you to configure multiple GNBD server nodes (nodes that export GNBDs to GFS nodes) to provide redundant paths to the storage devices. The GNBD server nodes, in turn, present multiple storage paths to GFS nodes via redundant GNBDs. When using GNBD with device-mapper multipath, if a GNBD server node becomes unavailable, another GNBD server node can provide GFS nodes with access to storage devices. If you are using GNBD with device-mapper multipath, you need to take the following into consideration: · Linux page caching, as desribed in Section 1, "Linux Page Caching". · Fencing GNBD server nodes, as described in Section 2, "Fencing GNBD Server Nodes". · GNBD device names; export names for GNBD devices must be unique. Additionally, you must specify the -u or -U when using the gnbd_export command. Exporting GNBD devices is described in Chapter 3, GNBD Driver and Command Usage. 1. Linux Page Caching For GNBD with device-mapper multipath, do not specify Linux page caching (the -c option of the gnbd_export command). All GNBDs that are part of a logical volume must run with caching disabled. [. . . ] When GNBDs are imported, device nodes are created for them in /dev/gnbd/ with the name assigned when they were exported. Usage gnbd_import -iServer Server Specifies a GNBD server by hostname or IP address from which to import GNBDs. All GNBDs exported from the server are imported on the client running this command. Example This example imports all GNBDs from the server named nodeA. gnbd_import -i nodeA 8 Chapter 4. Running GFS on a GNBD Server Node You can run GFS on a GNBD server node, with some restrictions. In addition, running GFS on a GNBD server node reduces performance. The following restrictions apply when running GFS on a GNBD server node. Important When running GFS on a GNBD server node you must follow the restrictions listed; otherwise, the GNBD server node will fail. 1. [. . . ]