You can list and set iSCSI parameters for software iSCSI and for dependent hardware iSCSI by using ESXCLI.

You can retrieve and set iSCSI parameters by running one of the following commands.

Parameter Type

Command

Adapter-level parameters

 
esxcli iscsi adapter param set --adapter=<vmhba> --key=<key> --value=<value>

Target-level parameters

 
esxcli iscsi adapter target portal param set --adapter=<vmhba> --key=<key> --value=<value> --address=<address> --name=<iqn.name>

Discovery-level parameters

 
esxcli iscsi adapter discovery sendtarget param set --adapter=<vmhba> --key=<key> --value=<value> --address=<address>

The following table lists all settable parameters. These parameters are also described in the IETF rfc 3720. You can run esxcli iscsi adapter param get to determine whether a parameter is settable or not.

The parameters in the table apply to software iSCSI and dependent hardware iSCSI.

Settable iSCSI Parameters

Parameter

Description

DataDigestType

Increases data integrity. When data digest is enabled, the system performs a checksum over each PDUs data part and verifies using the CRC32C algorithm.

Note

Systems that use Intel Nehalem processors offload the iSCSI digest calculations for software iSCSI, thus reducing the impact on performance.

Valid values are digestProhibited, digestDiscouraged, digestPreferred, or digestRequired.

HeaderDigest

Increases data integrity. When header digest is enabled, the system performs a checksum over the header part of each iSCSI Protocol Data Unit (PDU) and verifies using the CRC32C algorithm.

MaxOutstandingR2T

Max Outstanding R2T defines the Ready to Transfer (R2T) PDUs that can be in transition before an acknowledgement PDU is received.

FirstBurstLength

Maximum amount of unsolicited data an iSCSI initiator can send to the target during the execution of a single SCSI command, in bytes.

MaxBurstLength

Maximum SCSI data payload in a Data-In or a solicited Data-Out iSCSI sequence, in bytes.

MaxRecvDataSegLen

Maximum data segment length, in bytes, that can be received in an iSCSI PDU.

NoopOutInterval

Time interval, in seconds, between NOP-Out requests sent from your iSCSI initiator to an iSCSI target. The NOP-Out requests serve as the ping mechanism to verify that a connection between the iSCSI initiator and the iSCSI target is active.

Supported only at the initiator level.

NoopOutTimeout

Amount of time, in seconds, that can lapse before your host receives a NOP-In message. The message is sent by the iSCSI target in response to the NOP-Out request. When the NoopTimeout limit is exceeded, the initiator terminates the current session and starts a new one.

Supported only at the initiator level.

RecoveryTimeout

Amount of time, in seconds, that can lapse while a session recovery is performed. If the timeout exceeds its limit, the iSCSI initiator terminates the session.

DelayedAck

Allows systems to delay acknowledgment of received data packets.

You can use the following ESXCLI commands to list parameter options.

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Run esxcli iscsi adapter param get to list parameter options for the iSCSI adapter.

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Run esxcli iscsi adapter discovery sendtarget param get or esxcli iscsi adapter target portal param set to retrieve information about iSCSI parameters and whether they are settable.

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Run esxcli iscsi adapter discovery sendtarget param get or esxcli iscsi adapter target portal param set to set iSCSI parameter options.

If special characters are in the <name>=<value> sequence, for example, if you add a space, you must surround the sequence with double quotes ("<name> = <value>").