Red Hat GFS 6.0 -, Administrator'S Manual

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122 Chapter 11. Using GNBD
Note
A server should not import the GNBDs to use them as a client would. If a server exports the devices
uncached, they may also be used by
ccsd
and
gfs
.
11.1.1.1. Usage
gnbd_export -d pathname -e gnbdname [
-c
]
]
pathname
Specifies a storage device to export.
gnbdname
Specifies an arbitrary name selected for the GNBD. It is used as the device name on GNBD
clients. This name must be unique among all GNBDs exported in the network.
-o
Export the device as read-only.
Note
If a GNBD server that is exporting CCS files is also exporting GNBDs in multipath mode, it
must export the CCS files as read-only. Under those circumstances, a GNBD client cannot use
ccs_tool
to update its copy of the CCS files. Instead, the CCS files must be updated on a node
where the CCS files are stored locally or on FC-attached storage.
-c
Enable caching. Reads from the exported GNBD and takes advantage of the Linux page cache.
By default, the
gnbd_export
command does not enable caching.
Caution
For GNBD multipath, you must not specify the
-c
option. All GNBDs that are part of the pool
must run with caching disabled . Pool, the GFS volume manager, does not check for caching
being disabled; therefore, data corruption will occur if the GNBD devices are run with caching
enabled.
Note
If you have been using GFS 5.2 or earlier and do not want to change your GNBD setup you
should specify the
-c
option. Before GFS Release 5.2.1, Linux caching was enabled by default
for
gnbd_export
. If the
-c
option is not specified, GNBD runs with a noticeable performance
decrease. Also, if the
-c
option is not specified, the exported GNBD runs in timeout mode,
using the default timeout value (the
-t
option). For more information about the
gnbd_export
command and its options, see the
gnbd_export
man page.