How can I troubleshoot iSCSI connection issues? (DSM 6.x)

How can I troubleshoot iSCSI connection issues? (DSM 6.x)

Symptoms

You encounter issues when trying to make an iSCSI connection.

Diagnosis

There are several commonly encountered iSCSI connection problems:

  • The iSCSI Initiator cannot find an iSCSI target.
  • The iSCSI Initiator finds an iSCSI target but fails to connect to it.
  • The iSCSI Initiator connects to an iSCSI target but discovers no LUN.

Resolution

If the iSCSI Initiator cannot find an iSCSI target:

  1. In Windows iSCSI Initiator, go to Discovery > Discover Portal > Advanced Settings > General:
    • Specify the network interface to use for iSCSI connections if you have more than one network interfaces on both the initiator and target.
    • Make sure that Enable CHAP log on is not checked.1

If the iSCSI Initiator finds an iSCSI target but fails to connect to it:

  1. In Windows iSCSI Initiator, go to Targets > Connect > Advanced Settings:
    • Specify the network interface to use for iSCSI connections if you have more than one network interfaces on both the initiator and target.
    • Make sure that you entered identical name and password on DSM as the Name and Target secret in Windows iSCSI Initiator.
  2. On DSM, enable Allow multiple sessions if the iSCSI target is planned to be used as cluster aware storage such as VMFS, OCFS, etc. and needs to be connected to multiple hosts. Otherwise, an iSCSI target can only be connected to one host at a time.
  3. Make sure CRC checksum is disabled/enabled on both the initiator and iSCSI target.2 The settings on both sides must be identical for the connection to work.

If the iSCSI Initiator connects to an iSCSI target but discovers no LUN:

  1. On DSM, go to iSCSI Manager > LUN to make sure that you have mapped the iSCSI LUNs to the iSCSI target.
  2. On the Target page, select the iSCSI target and click Action > Edit. Under Masking, make sure the permission is Read/Write or Read Only for the iSCSI Initiator to access the iSCSI LUNs.

Notes:

  1. If you wish to ensure connection security with CHAP, you can check Enable CHAP log on when connecting to an iSCSI target under Targets in Windows iSCSI Initiator.
  2. Running the CRC checksum may affect system performance, so we do not recommend enabling this option unless necessary.
Symptoms
Diagnosis
Resolution
If the iSCSI Initiator cannot find an iSCSI target:
If the iSCSI Initiator finds an iSCSI target but fails to connect to it:
If the iSCSI Initiator connects to an iSCSI target but discovers no LUN: