User Manual

Rev 2.1-1.0.6
Mellanox Technologies
47
4.1.2.1.1 SRP Module Parameters
When loading the SRP module, the following parameters can be set (viewable by the "modinfo
ib_srp"
command):
Constraints between parameters:
•
dev_loss_tmo, fast_io_fail_tmo, reconnect_delay cannot be all disabled or neg-
ative values.
•
reconnect_delay must be positive number.
•
fast_io_fail_tmo must be smaller than SCSI block device timeout.
•
fast_io_fail_tmo must be smaller than dev_loss_tmo.
4.1.2.1.2 SRP Remote Ports Parameters
Several SRP remote ports parameters are modifiable online on existing connection.
 To modify dev_loss_tmo to 600 seconds:
 To modify fast_io_fail_tmo to 15 seconds:
 To modify reconnect_delay to 10 seconds:
cmd_sg_entries Default number of gather/scatter entries in the SRP command (default is
12, max 255)
allow_ext_sg Default behavior when there are more than cmd_sg_entries S/G entries
after mapping; fails the request when false (default false)
topspin_workarounds Enable workarounds for Topspin/Cisco SRP target bugs
reconnect_delay Time between successive reconnect attempts. Time between successive
reconnect attempts of SRP initiator to a disconnected target until
dev_loss_tmo timer expires (if enabled), after that the SCSI target will
be removed.
fast_io_fail_tmo Number of seconds between the observation of a transport layer error
and failing all I/O. Increasing this timeout allows more tolerance to
transport errors, however, doing so increases the total failover time in
case of serious transport failure.
Note: fast_io_fail_tmo value must be smaller than the value of
reconnect_delay.
dev_loss_tmo Maximum number of seconds that the SRP transport should insulate
transport layer errors. After this time has been exceeded the SCSI target
is removed. Normally it is advised to set this to -1 (disabled) which will
never remove the scsi_host. In deployments where different SRP targets
are connected and disconnected frequently, it may be required to enable
this timeout in order to clean old scsi_hosts representing targets that no
longer exists.
echo 600 > /sys/class/srp_remote_ports/port-xxx/dev_loss_tmo
echo 15 > /sys/class/srp_remote_ports/port-xxx/fast_io_fail_tmo
echo 20 > /sys/class/srp_remote_ports/port-xxx/reconnect_delay