Managing I/O In Error Situations; Section 5.15, "Managing I/O In Error Situations - Novell LINUX ENTERPRISE SERVER 10 - STORAGE ADMINISTRATION GUIDE 7-2007 Administration Manual

5 Repeat
6 Run the Multipath tool to recognize the devices for DM-MPIO configuration. At a terminal

5.15 Managing I/O in Error Situations

You might need to configure multipathing to queue I/O if all paths fail concurrently. In certain
scenarios, where the driver, the HBA, or the fabric experiences spurious errors, it is advisable that
DM-MPIO be configured to queue all I/O where those errors lead to a loss of all paths, and never
propagate errors upwards. Because this will lead to I/O being queued indefinitely unless a path is
reinstated, make sure that multipathd is running and works for your scenario. Otherwise, I/O
might be stalled forever on the affected multipathed device, until reboot or until you manually return
to failover instead of queuing.
To test the scenario:
1 In a terminal console, log in as the root user.
2 Activate queuing instead of failover for the device I/O by entering (all on the same line):
3 Return to failover for the device I/O by entering (all on the same line):
To set up queuing I/O for scenarios where all paths fail:
1 In a terminal console, log in as the root user.
2 Open the /etc/multipath.conf file in a text editor.
3 Uncomment the defaults section and its ending bracket, then add the default_features
4 When you are ready to return over to failover for the device I/O, enter (all on the same line):
56 SLES 10 Storage Administration Guide
Feb 14 01:03 multipathd: mpath4: event checker started
Feb 14 01:03 multipathd: mpath5: event checker started
Feb 14 01:03:multipathd: mpath4: remaining active paths: 1
Feb 14 01:03 multipathd: mpath5: remaining active paths: 1
Step 2 through Step 4
that are connected to the new device.
console prompt, enter
multipath
You can now configure the new device for multipathing.
dmsetup message 3600601607cf30e00184589a37a31d911 0
queue_if_no_path
Replace the UUID (3600601607cf30e00184589a37a31d911) with the UUID for your
device.
dmsetup message 3600601607cf30e00184589a37a31d911 0
fail_if_no_path
Replace the UUID (3600601607cf30e00184589a37a31d911) with the UUID for your
device.
This command immediately causes all queued I/O to fail.
setting, as follows:
defaults {
default_features "1 queue_if_no_path"
}
dmsetup message mapname 0 fail_if_no_path
to add paths through other HBA adapters on the Linux system