Adding/Removing A Logical Unit Through Rescan-Scsi-Bus.sh; Modifying Link Loss Behavior - Red Hat ENTERPRISE LINUX 5.5 - ONLINE STORAGE GUIDE Manual

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dmsetup suspend multipath_device

Open the device mapper table you saved earlier (i.e. table_name). Change the second number

(i.e. the disk end sector) to reflect the new number of 512 byte sectors in the disk. For example, if

the new disk size is 2GB, change the second number to 4194304.

Reload the modified device mapper table:

dmsetup reload multipath_device table_name

Resume the device mapper target:

dmsetup resume multipath_device

For more information about multipathing, refer to the

www.redhat.com/docs/manuals/enterprise/).

15. Adding/Removing a Logical Unit Through rescan-scsi-

bus.sh

The sg3_utils package provides the rescan-scsi-bus.sh script, which can automatically

update the logical unit configuration of the host as needed (after a device has been added to the

system). The rescan-scsi-bus.sh script can also perform an issue_lip on supported devices.

For more information about how to use this script, refer to rescan-scsi-bus.sh --help.

To install the sg3_utils package, run yum install sg3_utils.

Known Issues With rescan-scsi-bus.sh

When using the rescan-scsi-bus.sh script, take note of the following known issues:

• In order for rescan-scsi-bus.sh to work properly, LUN0 must be the first mapped logical unit.

The rescan-scsi-bus.sh can only detect the first mapped logical unit if it is LUN0. The rescan-

scsi-bus.sh will not be able to scan any other logical unit unless it detects the first mapped

logical unit even if you use the --nooptscan option.

• A race condition requires that rescan-scsi-bus.sh be run twice if logical units are mapped for

the first time. During the first scan, rescan-scsi-bus.sh only adds LUN0; all other logical units

are added in the second scan.

• A bug in the rescan-scsi-bus.sh script incorrectly executes the functionality for recognizing a

change in logical unit size when the --remove option is used.

• The rescan-scsi-bus.sh script does not recognize ISCSI logical unit removals.

16. Modifying Link Loss Behavior

This section describes how to modify the link loss behavior of devices that use either fibre channel or

iSCSI protocols.

http://www.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5.4/html/DM_Multipath/index.html