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Definitions for iSCSI statistics

You can obtain the iSCSI statistics that are displayed when you run the iscsi stats command. For vFiler contexts, the statistics displayed refer to the entire storage system, not the individual vFiler units.

iSCSI PDUs received

The iSCSI Protocol Data Units (PDUs) sent by the initiator include the following statistics:

SCSI-CMD
SCSI-level command descriptor blocks.
LoginReq
Login request PDUs sent by initiators during session setup.
DataOut
PDUs containing write operation data that did not fit within the PDU of the SCSI command. The PDU maximum size is set by the storage system during the operation negotiation phase of the iSCSI login sequence.
Nop-Out
A message sent by initiators to check whether the target is still responding.
Logout-Req
Request sent by initiators to terminate active iSCSI sessions or to terminate one connection of a multi-connection session.
SNACK
A PDU sent by the initiator to acknowledge receipt of a set of DATA_IN PDUs or to request retransmission of specific PDUs.
SCSI TaskMgtCmd
SCSI-level task management messages, such as ABORT_TASK and RESET_LUN.
Text-Req
Text request PDUs that initiators send to request target information and renegotiate session parameters.

iSCSI PDUs transmitted

The iSCSI PDUs sent by the storage system include the following statistics:

SCSI-Rsp
SCSI response messages.
LoginRsp
Responses to login requests during session setup.
DataIn
Messages containing data requested by SCSI read operations.
Nop-In
Responses to initiator Nop-Out messages.
Logout-Rsp
Responses to Logout-Req messages.
R2T
Ready to transfer messages indicating that the target is ready to receive data during a SCSI write operation.
SCSI TaskMgtRsp
Responses to task management requests.
TextRsp
Responses to Text-Req messages.
Asyncmsg
Messages the target sends to asynchronously notify the initiator of an event, such as the termination of a session.
Reject
Messages the target sends to report an error condition to the initiator, for example:
  • Data Digest Error (checksum failed)
  • Target does not support command sent by the initiator
  • Initiator sent a command PDU with an invalid PDU field

iSCSI CDBs

You can obtain statistics associated with handling iSCSI Command Descriptor Blocks, including the number of blocks of data transferred, and the number of SCSI-level errors and successful completions.

iSCSI Errors

You can obtain a list of login failures and other SCSI protocol errors.