Installation guide

Chapter 3. GNBD Driver and Command Usage
The Global Network Block Device (GNBD) driver allows a node to export its local storage as a GNBD
over a network so that other nodes on the network can share the storage. Client nodes importing the
GNBD use it like any other block device. Importing a GNBD on multiple clients forms a shared storage
configuration through which GFS can be used.
The GNBD driver is implemented through the following components.
gnbd_serv — Implements the GNBD server. It is a user-space daemon that allows a node to export
local storage over a network.
gnbd.ko — Implements the GNBD device driver on GNBD clients (nodes using GNBD devices).
Two user commands are available to configure GNBD:
gnbd_export (for servers) — User program for creating, exporting, and managing GNBDs on a
GNBD server.
gnbd_import (for clients) — User program for importing and managing GNBDs on a GNBD client.
3.1. Exporting a GNBD from a Server
The gnbd_serv daemon must be running on a node before it can export storage as a GNBD. You can
start the gnbd_serv daemon running gnbd_serv as follows:
#gnbd_serv
gnbd_serv: startup succeeded
Once local storage has been identified to be exported, the gnbd_export command is used to export it.
Warning
When you configure GNBD servers with device-mapper multipath, you must not use page
caching. All GNBDs that are part of a logical volume must run with caching disabled. By default,
the gnbd_export command exports with caching turned off.
Note
A server should not import the GNBDs to use them as a client would. If a server exports the
devices uncached, the underlying devices may also be used by gfs.
Usage
gnbd_expo rt -d pathname -e gnbdname [-c][-u][-U
pathname
Specifies a storage device to export.
gnbdname
Red Hat Enterprise Linux 4 Global Network Block Device
10