Dell Emulex Family of Adapters - Manual (Page 1031)

Emulex Drivers Version 10.2 for VMware ESXi User Manual P010087-01A Rev. A
3. Configuration
iSCSI Driver Configuration
1031
iSCSI Error Handling
The goal of iSCSI error handling is to be tolerant of link level and/or target level
failures up to configured timeout values so that I/O errors are not seen by the
application or operating system. The error handling is triggered under the following
conditions:

Loss of immediate link to the initiator (for example, cable disconnect/port
failure).
The firmware detects and notifies the driver of a loss of the link. When this
happens, the driver will queue the I/O requests internally up to a configured
timeout period so that the operating system does not see I/O errors. This
timeout is known as LDTO.

Loss of connection to the target due to target or network disconnection at the
target.
If the driver has I/O requests pending with the target and the target becomes
unavailable (due to target going down or failing over, or network issues at the
target), the driver queues up the I/O request internally up to a configured
timeout period. This timeout is known as ETO.
When the configured threshold for LDTO and ETO is reached and the initiator is still
unable to connect to the target, the driver fails all I/O requests. At this point, I/O errors
will be seen by the application and operating system.
Note: Following a link up, switch ports can take a long time to initialize and go to a
forwarding state. Because of this, additional time should be added to the ETO
and LDTO settings to eliminate I/O disruption and/or target unavailability. If
the switch port is connected to a single host, then PortFast mode can be enabled
on the switch port to eliminate delays in transitioning to a forwarding state.
Configuring LDTO and ETO on ESXi Server
The following table lists the default values of LDTO and ETO on ESXi Server and the
limits within which they can be configured.
Note: If the value of ETO is set to a number between 0 and 19, the driver will assume a
value of 20 seconds internally. You will not see any modification to the registry.
LDTO and ETO values are configurable during insmod time. The ETO value specified
during insmod is the default ETO value that is applied to all targets.
The following command line shows how to configure the driver with LDTO value as 25
seconds:
Table 3-7 LDTO and ETO Default Values on ESX Server
Parameter
Default
Value
Minimum
Value
Maximum
Value
LDTO 20 seconds 0 seconds 3600 seconds
ETO 30 30 seconds 0 seconds 3600 seconds