iscsid.conf

iscsid.conf is the configuration file for iscsid, the daemon responsible for managing iSCSI connections (Internet Small Computer Systems Interface). iSCSI is a network protocol used to link data storage devices over a network, allowing servers to access storage as if it were directly attached. This configuration file contains settings that define how iscsid operates and handles iSCSI targets and sessions.

Purpose

• Configure iSCSI Daemon (iscsid): The iscsid.conf file provides control over various parameters related to iSCSI connections, including timeouts, discovery mechanisms, authentication, and session management.

• Fine-tune iSCSI Initiator Behavior: Allows system administrators to customize iSCSI session behavior, error recovery, authentication methods, and security features for each target or global session.

Common Configuration Parameters

1. node.startup Defines how sessions are started.

   • manual: Sessions are started manually.

   • automatic: Sessions are automatically started during boot.

   node.startup = automatic

2. node.session.auth.authmethod Authentication method to use for iSCSI sessions. Common values:

   • CHAP: Challenge Handshake Authentication Protocol.

   • None: No authentication.

   node.session.auth.authmethod = CHAP

3. node.session.auth.username Username for CHAP authentication (if CHAP is enabled).

   node.session.auth.username = iscsiuser

4. node.session.auth.password Password for CHAP authentication (if CHAP is enabled).

   node.session.auth.password = mypassword

5. node.session.timeo.replacement_timeout Defines the timeout period (in seconds) before an iSCSI session tries to reconnect after a failure.

   node.session.timeo.replacement_timeout = 120

6. node.conn[0].timeo.login_timeout Defines the maximum time (in seconds) to wait for a successful login to an iSCSI target.

   node.conn[0].timeo.login_timeout = 15

7. node.conn[0].timeo.logout_timeout Specifies the time (in seconds) to wait for a successful logout from the iSCSI target.

   node.conn[0].timeo.logout_timeout = 15

8. discovery.sendtargets.iscsi.MaxRecvDataSegmentLength Specifies the maximum amount of data (in bytes) that the initiator is willing to receive from the target in a single data segment during discovery.

   discovery.sendtargets.iscsi.MaxRecvDataSegmentLength = 32768

9. node.session.nr_sessions Defines the maximum number of sessions that can be established to a single target.

   node.session.nr_sessions = 1

10. node.conn[0].iscsi.MaxXmitDataSegmentLength Defines the maximum data segment size (in bytes) that the initiator can send in a single iSCSI PDU (Protocol Data Unit).

    node.conn[0].iscsi.MaxXmitDataSegmentLength = 32768

Example Configuration

Here is a sample iscsid.conf configuration that sets up CHAP authentication and session management with a login timeout of 15 seconds and automatic startup of the session.

# Enable CHAP authentication
node.session.auth.authmethod = CHAP
node.session.auth.username = iscsiuser
node.session.auth.password = securepassword

# Session timeout settings
node.session.timeo.replacement_timeout = 120
node.conn[0].timeo.login_timeout = 15
node.conn[0].timeo.logout_timeout = 15

# Data segment settings
node.conn[0].iscsi.MaxXmitDataSegmentLength = 32768
discovery.sendtargets.iscsi.MaxRecvDataSegmentLength = 32768

# Startup settings
node.startup = automatic

Key Sections of iscsid.conf

1. Authentication The authentication section allows you to configure CHAP or other methods for secure connections between initiators and targets.

2. Timeouts Timeout settings control how long the iSCSI daemon waits for operations like login, logout, or session recovery.

3. Session Management Configuration options allow you to define how iSCSI sessions are started, whether they are manual or automatic, and how many sessions can be established with a given target.

4. Data Segment Settings These settings define how much data can be transmitted or received in a single data segment, impacting performance.

Best Practices

• Security: Use CHAP or another secure authentication method, especially in untrusted networks, to ensure secure communication between initiators and targets.

• Timeout Adjustments: Adjust timeouts based on your network environment. Lower timeouts may be better in stable networks, while higher timeouts may be required in environments with latency or instability.

• Monitor Sessions: Regularly monitor iSCSI sessions using iscsiadm to ensure stability and proper function, especially after modifying iscsid.conf.

Conclusion

iscsid.conf provides detailed control over iSCSI session behavior, authentication, and timeouts, enabling administrators to tailor the iSCSI initiator for their specific network environment. Proper configuration ensures secure and reliable access to iSCSI storage resources.