Red Hat ENTERPRISE LINUX 5 - GLOBAL NETWORK BLOCK DEVICE Bedienungsanleitung PDF herunterladen (Seite 12)

The UID is used by device-mapper multipath to determine which devices belong in a mul-

tipath map. A device must have a UID to be multipathed. However, for most SCSI devices

the default Get UID command, /usr/sbin/gnbd_get_uid, will return an appropriate value.

Note

The UID refers to the device being exported, not the GNBD itself. The UIDs of

two GNBD devices should be equal, only if they are exporting the same under-

lying device. This means that both GNBD servers are connected to the same

physical device.

Warning

This option should only be used for exporting shared storage devices, when

the -Ucommand option does not work. This should almost never happen for SCSI

devices. If two GNBD devices are not exporting the same underlying device,

but are given the same UID, data corruption will occur.

-UCommand

Gets the UID command. The UID command is a command the gnbd_export command will

run to get a Universal Identifier for the exported device. The UID is necessary to use device-

mapper multipath with GNBD. The command must use the full path of any executeable that

you wish to run. A command can contain the %M, %m or %n escape sequences. %M will

be expanded to the major number of the exported device, %m will be expaned to the minor

number of the exported device, and %n will be expanded to the sysfs name for the device.

If no command is given, GNBD will use the default command /usr/sbin/gnbd_get_uid. This

command will work for most SCSI devices.

Examples

This example is for a GNBD server configured with GNBD multipath. It exports device /dev/sdc2

as GNBD gamma. Cache is disabled by default.

gnbd_export -d /dev/sdc2 -e gamma -U

This example is for a GNBD server not configured with GNBD multipath. It exports device /

dev/sdb2 as GNBD delta with cache enabled.

gnbd_export -d /dev/sdb1 -e delta -c

This example exports device /dev/sdb2 as GNBD delta with cache enabled.

gnbd_export -d /dev/sdb2 -e delta -c

2. Importing a GNBD on a Client

Examples

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Red Hat ENTERPRISE LINUX 5 - GLOBAL NETWORK BLOCK DEVICE Bedienungsanleitung Seite 12