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ESX Configuration Guide

Configuring Additional Parameters for iSCSI

You might need to configure additional parameters for your iSCSI initiators. For example, some iSCSI storage systems require ARP (Address Resolution Protocol) redirection to move iSCSI traffic dynamically from one port to another. In this case, you must activate ARP redirection on your host.

Table 8-2 lists advanced iSCSI parameters that you can configure using the vSphere Client. In addition, you can use the vicfg-iscsi vSphere CLI command to configure some of the advanced parameters. For information, see the vSphere Command-Line Interface Installation and Scripting Guide and vSphere Command-Line Interface Reference.

Do not make any changes to the advanced iSCSI settings unless you are working with the VMware support team or otherwise have thorough information about the values to provide for the settings.

Table 8-2. Additional Parameters for iSCSI Initiators

Advanced Parameter

Description

Configurable On

 

 

 

Header Digest

Increases data integrity. When header digest is enabled, the system

Software iSCSI

 

performs a checksum over each iSCSI Protocol Data Unit’s (PDU’s)

Dependent Hardware

 

header part and verifies using the CRC32C algorithm.

iSCSI

 

 

 

Data Digest

Increases data integrity. When data digest is enabled, the system

Software iSCSI

 

performs a checksum over each PDU's data part and verifies using

Dependent Hardware

 

the CRC32C algorithm.

iSCSI

 

NOTE Systems that use Intel Nehalem processors offload the iSCSI

 

 

digest calculations for software iSCSI, thus reducing the impact on

 

 

performance.

 

 

 

 

Maximum

Defines the R2T (Ready to Transfer) PDUs that can be in transition

Software iSCSI

Outstanding R2T

before an acknowledge PDU is received.

Dependent Hardware

 

 

iSCSI

 

 

 

First Burst Length

Specifies the maximum amount of unsolicited data an iSCSI initiator

Software iSCSI

 

can send to the target during the execution of a single SCSI command,

Dependent Hardware

 

in bytes.

iSCSI

 

 

 

Maximum Burst

Maximum SCSI data payload in a Data-In or a solicited Data-Out

Software iSCSI

Length

iSCSI sequence, in bytes.

Dependent Hardware

 

 

iSCSI

 

 

 

Maximum Receive

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

Software iSCSI

Data Segment Length

iSCSI PDU.

Independent Hardware

 

 

iSCSI

 

 

 

Session Recovery

Specifies the amount of time, in seconds, that can lapse while a session

Software iSCSI

Timeout

recovery is performed. If the timeout exceeds its limit, the iSCSI

Dependent Hardware

 

initiator terminates the session.

iSCSI

 

 

 

No-Op Interval

Specifies the time interval, in seconds, between NOP-Out requests

Software iSCSI

 

sent from your iSCSI initiator to an iSCSI target. The NOP-Out

Dependent Hardware

 

requests serve as the ping mechanism to verify that a connection

iSCSI

 

between the iSCSI initiator and the iSCSI target is active.

 

No-Op Timeout

Specifies the 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 no-op timeout

 

limit is exceeded, the initiator terminates the current session and starts

 

a new one.

Software iSCSI

Dependent Hardware iSCSI

104

VMware, Inc.

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