System information

Pro ced u re 25.8. Det ermin in g T h e St at e o f a Remo t e Po rt
1. To determine the state of a remote port, run the following command:
$ cat
/sys/class/fc_remote_port/rport-H:B:R/port_state
2. This command will return Bl o cked when the remote port (along with devices accessed
through it) are blocked. If the remote port is operating normally, the command will return
O nl i ne.
3. If the problem is not resolved within d ev_l o ss_tmo seconds, the rport and devices will be
unblocked and all I/O running on that device (along with any new I/O sent to that device) will
be failed.
Pro ced u re 25.9 . Ch an g in g d ev_l o ss_tmo
To change the d ev_l o ss_tmo value, echo in the desired value to the file. For example, to set
d ev_l o ss_tmo to 30 seconds, run:
$ echo 30 >
/sys/class/fc_remote_port/rport-H:B:R/dev_loss_tmo
For more information about d ev_l o ss_tmo , refer to Section 25.1.1, “ Fibre Channel API” .
When a link or target port loss exceeds d ev_l o ss_tmo , the scsi _d evi ce and sd N devices are
removed. The target port SCSI ID binding is saved. When the target returns, the SCSI address and
sd Nassignments may be changed. The SCSI address will change if there has been any LUN
configuration changes behind the target port. The sd N names may change depending on timing
variations during the LUN discovery process or due to LUN configuration change within storage.
These assignments are not persistent as described in Section 25.3, “ Persistent Naming” . Refer to
section Section 25.3, “ Persistent Naming” for alternative device naming methods that are persistent.
25.16.2. iSCSI Set t ings Wit h d m-mul ti path
If d m-mul ti path is implemented, it is advisable to set iSCSI timers to immediately defer commands
to the multipath layer. To configure this, nest the following line under d evi ce { in
/etc/mul ti path. co nf:
features "1 queue_if_no_path"
This ensures that I/O errors are retried and queued if all paths are failed in the d m-mul ti path layer.
You may need to adjust iSCSI timers further to better monitor your SAN for problems. Available iSCSI
timers you can configure are NOP-Out Interval/Timeouts and repl acement_ti meo ut, which are
discussed in the following sections.
25.1 6 .2 .1 . NOP-Out Int e rval/T im eo ut
To help monitor problems the SAN, the iSCSI layer sends a NOP-Out request to each target. If a NOP-
Out request times out, the iSCSI layer responds by failing any running commands and instructing the
SCSI layer to requeue those commands when possible.
Known Issues Wit h rescan- scsi- bus.sh
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