Persistent Naming - Red Hat ENTERPRISE LINUX 5.5 - ONLINE STORAGE GUIDE Manual

Online Storage Guide
This command displays the session/device state, session ID (sid), some negotiated parameters, and
the SCSI devices accessible through the session.
For shorter output (for example, to display only the sid-to-node mapping), run:
iscsiadm -m session -P 0
or
iscsiadm -m session
These commands print the list of running sessions with the format:
driver [sid] target_ip:port,target_portal_group_tag proper_target_name
For example:
iscsiadm -m session
tcp [2] 10.15.84.19:3260,2 iqn.1992-08.com.netapp:sn.33615311
tcp [3] 10.15.85.19:3260,3 iqn.1992-08.com.netapp:sn.33615311
For more information about the iSCSI API, refer to /usr/share/doc/iscsi-initiator-
utils-version/README.

4. Persistent Naming

The operating system issues I/O to a storage device by referencing the path that is used to reach it.
For SCSI devices, the path consists of the following:
• PCI identifier of the host bus adapter (HBA)
• channel number on that HBA
• the remote SCSI target address
• the Logical Unit Number (LUN)
This path-based address is not persistent. It may change any time the system is reconfigured (either
by on-line reconfiguration, as described in this manual, or when the system is shutdown, reconfigured,
and rebooted). It is even possible for the path identifiers to change when no physical reconfiguration
has been done, as a result of timing variations during the discovery process when the system boots, or
when a bus is re-scanned.
The operating system provides several non-persistent names to represent these access paths
to storage devices. One is the /dev/sd name; another is the major:minor number. A third is
a symlink maintained in the /dev/disk/by-path/ directory. This symlink maps from the path
identifier to the current /dev/sd name. For example, for a Fibre Channel device, the PCI info and
Host:BusTarget:LUN info may appear as follows:
pci-0000:02:0e.0-scsi-0:0:0:0 -> ../../sda
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