iSCSI Session Information

The iSCSI Session Information page displays information about a selected initiator. For general descriptions of each field, see RFC 3720 at http://www.apps.ietf.org/rfc/rfc3720.html.

By default, the iSCSI Session Information page displays session connection information. To modify the information displayed, click one of the following buttons:

• Show Commands–Display commands executing at the time the iSCSI Session Information page was requested.

Note: The Active Commands section displays commands that were executing at the time the iSCSI Session Information page was requested. If the session is not busy, there might not be any currently executing commands to display.

• Show Session Parameters–Display session-wide parameters for the selected initiator.

• Show Connections–Display the connections and connection parameters associated with this session.

• Show All–Display all categories of session information.

• Show All–Display all categories of session information

As you review session information for the selected initiator, consider the following best practices:

• Local Interface–The interface on the filer used by the TCP connection.

Filers support the iSCSI service over all Ethernet interfaces. By default, the iSCSI service is enabled on all Ethernet interfaces after you enable the license. For filers with available Gigabit Ethernet interfaces, it is recommended that you do not use any 10/100 Megabit management interfaces for iSCSI communication.

• Header Digest Enabled/Data Digest Enabled–Indicates whether the digests are enabled for this session.

Enabling header or data digests can adversely impact performance, and the TCP checksums provide adequate data integrity benefits for most situations. Enable the digests only if the network is unreliable with no alternative data-integrity method (for example, IPsec).

• Authentication Method–The authentication method for this session. The authentication methods supported by Data ONTAP are none, deny, and CHAP.

• If all the initiators logging into the filer run within your trusted network, select none for the initiator authentication method.

• If the filer is part of a public network, consider using CHAP for the initiator authentication method.

• If you want to prevent access from a specific initiator, select deny for the authentication method.

• TCP Receive Window Size–The TCP receive window size for the filer for this connection.

The default size is 131,400 bytes. Do not change this value except under the direction of support or service personnel.

• Initiator Max Recv Data Segment–The maximum data segment length in bytes that the initiator declares it can receive. Targets are required to send PDUs with a data segment that does not exceed this value. The default is 8192 bytes.

Different initiators may advertise different data segment lengths. If you know in advance what your traffic pattern will be, consider reconfiguring this value to a more efficient length for your situation.

• Max Connections–The maximum number of connections allowed for the session as negotiated by the initiator and the target. The default is 1.

If you are using a Data ONTAP-qualified initiator that supports multiple connections, consider configuring Data ONTAP to use multiple iSCSI connections. For details, see the Data ONTAP Block Access Management Guide for iSCSI and FCP.

• Error Recovery Level–The error recovery level negotiated by the initiator and the target at connection time. The default is 0.

Data ONTAP 7.1 and later supports error recovery levels 0, 1, and 2:

• 0–When a connection is lost, all commands on that connection are aborted. Typically, the initiator terminates the whole session and initiates a new session.

• 1–A iSCSI data digest (checksum) error that can be retried without losing the connection or aborting a SCSI command.

• 2–SCSI commands can survive the loss of an individual TCP connection.

To enable error recovery levels 1 or 2, see the Data ONTAP Block Access Management Guide for iSCSI and FCP.

• Immediate Data Enabled–Indicates whether immediate data is supported, as negotiated by the initiator and the target.

Data ONTAP supports immediate data up to 64K. If your initiator software supports immediate data, it is recommended that you take advantage of the efficiencies of using immediate data.

• Command Window Size–Indicates the maximum number of I/Os that can be on this iSCSI session at one time. The default setting for this field is based on the filer's memory size, as follows:

The default command window size is recommended for most environments. Increasing the command window size may result in improved performance for a given host, especially if the host is generating a heavy load of uncached read requests. However, increasing the command window size may also reduce the number of hosts that a filer can service simultaneously.

You can configure the per-session limit with the options iscsi.iswt.max_ios_per_session command.