iscsi超时设置

24.16.3. iSCSI Root

When accessing the root partition directly through an iSCSI disk, the iSCSI timers should be set so that iSCSI layer has several chances to try to reestablish a path/session. In addition, commands should not be quickly re-queued to the SCSI layer. This is the opposite of what should be done when dm-multipath is implemented.

To start with, NOP-Outs should be disabled. You can do this by setting both NOP-Out interval and timeout to zero. To set this, open/etc/iscsi/iscsid.conf and edit as follows:

node.conn[0].timeo.noop_out_interval = 0node.conn[0].timeo.noop_out_timeout = 0

In line with this, replacement_timeout should be set to a high number. This will instruct the system to wait a long time for a path/session to reestablish itself. To adjustreplacement_timeout, open /etc/iscsi/iscsid.conf and edit the following line:

node.session.timeo.replacement_timeout = replacement_timeout

After configuring /etc/iscsi/iscsid.conf, you must perform a re-discovery of the affected storage. This will allow the system to load and use any new values in/etc/iscsi/iscsid.conf. For more information on how to discover iSCSI devices, refer toSection 24.12, “ Scanning iSCSI Interconnects”.

Configuring Timeouts for a Specific Session

You can also configure timeouts for a specific session and make them non-persistent (instead of using/etc/iscsi/iscsid.conf). To do so, run the following command (replace the variables accordingly):

# iscsiadm -m node -T target_name -p target_IP:port -o update -n node.session.timeo.replacement_timeout -v $timeout_value