Managing I/O In Error Situations; Resolving Stalled I/O; Section 5.10, "Managing I/O In Error Situations; Section 5.11, "Resolving Stalled I/O - Novell LINUX ENTERPRISE SERVER 10 - STORAGE ADMINISTRATION GUIDE FOR EVMS Administration Manual

7 Save your changes, then close the file.

5.10 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 IO where those errors lead to a loss of all paths, and never
propagate errors upwards. As this will lead to IO being queued forever, unless a path is reinstated,
make sure that multipathd is running and works for your scenario. Otherwise, IO might be
stalled forever on the affected MPIO 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):

5.11 Resolving Stalled I/O

If all paths fail concurrently and I/O is queued and stalled, do the following:
1 Enter the following command at a terminal console prompt:
50 SLES 10 Storage Administration Guide for EVMS
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
Replace the mapname (such as 3600601607cf30e00184589a37a31d911) with the map
name for the device.
This command immediately causes all queued I/O to fail and propagates the error to the calling
application.