Fibre Channel over Ethernet

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Cisco Systems
FCoE fabric module
Original author(s) Joe Eykholt
Kiran Patil
Developer(s) Cisco Systems, Inc.
Initial release July 21, 2011 (2011-07-21)
Stable release 4.1.0 / June 20, 2012;
5 years ago (2012-06-20)
Preview release 4.2.0-rc5 / June 28, 2012;
4 years ago (2012-06-28)
Development status Production
Written in C
Operating system Linux
Type Fabric module
License GNU General Public License, version 2 (GPLv2)
Website www.cisco.com
See LIO for a complete overview over all fabric modules.

Fibre Channel over Ethernet (FCoE) provides FCoE SAN connectivity over Ethernet networks.

Contents

Overview

The FCoE fabric module provides Fibre Channel (FC) access over Ethernet. It is based on a fabric module from open-fcoe.org. The Open-FCoE target code was adapted to use a modified upstream Linux libfc module. This includes a patch series to re-enable point-to-point module for libfc (merged upstream), and a set of hooks into libfc to be able to hand off incoming FLOGI requests to Fibre Channel based LinuxIO modules.

Hardware support

The following Ethernet NICs are supported:

The fabric module (tcm_fc.ko, Linux kernel driver database) for LIO was released with Linux kernel 3.0 on July 21, 2011 (2011-07-21).[1]

targetcli

targetcli from Datera, Inc. is used to configure FCoE targets. targetcli aggregates service modules via a core library, and exports them through an API to the LIO, to provide a unified single-node SAN configuration shell, independently of the underlying fabric(s).

LIO Admin Manual
The LIO Admin Manual provides comprehensive background and many examples on using targetcli and on programming the Datera library.

Cheat sheet

Command Comment
/backstores/iblock create my_disk /dev/sdb Create the LUN my_disk on the block device /dev/sdb
/tcm_fc create <WWPN> Create a FCoE target
In /tcm_fc/<WWPN>:
luns/ create /backstores/iblock/my_disk 		Export the LUN my_disk
In /tcm_fc/<WWPN>:
acls/ create <Initiator WWPN> 		Allow access for the initiator at <WWPN>
/saveconfig Commit the configuration

Startup

targetcli is invoked by running targetcli as root from the command prompt of the underlying LIO shell. 

# targetcli
Welcome to targetcli:

 Copyright (c) 2014 by Datera, Inc.
 All rights reserved.

Visit us at http://www.datera.io.

Using ib_srpt fabric module.
Using qla2xxx fabric module.
Using iscsi fabric module.
Using loopback fabric module.
Using tcm_fc fabric module.

/> tcm_fc/ info 
Fabric module name: tcm_fc
ConfigFS path: /sys/kernel/config/target/fc
Allowed WWN list type: free
sysFabric module specfile: /var/target/fabric/tcm_fc.spec
Fabric module features: acls
Corresponding kernel module: tcm_fc
/>

Upon targetcli initialization, the underlying RTSlib loads the installed fabric modules, and creates the corresponding ConfigFS mount points (at /sys/kernel/config/target/<fabric>), as specified by the associated spec files (located in /var/target/fabric/fabric.spec).

Display the object tree

Use ls to list the object hierarchy, which is initially empty: 

/> ls
o- / ..................................................................... [...]
  o- backstores .......................................................... [...]
  | o- fileio ............................................... [0 Storage Object]
  | o- iblock ............................................... [0 Storage Object]
  | o- pscsi ................................................ [0 Storage Object]
  | o- rd_dr ................................................ [0 Storage Object]
  | o- rd_mcp ............................................... [0 Storage Object]
  o- ib_srpt ........................................................ [0 Target]
  o- iscsi .......................................................... [0 Target]
  o- loopback ....................................................... [0 Target]
  o- qla2xxx ........................................................ [0 Target]
/>
Global parameter auto_cd_after_create
After the creation of a new object, automatically enter its object context.

Per default, auto_cd_after_create is set to true, which automatically enters an object context (or working directory) after its creation. The examples here are modeled after this behavior.

Optionally, set auto_cd_after_create=false to prevent targetcli from automatically entering new object contexts after their creation: 

/> set global auto_cd_after_create=false
Parameter auto_cd_after_create is now 'false'.
/>

Create a backstore

Create a backstore using the IBLOCK or FILEIO type devices.

For instance, enter the top-level backstore context and create an IBLOCK backstore from a /dev/sdb block device: 

/> cd backstores/
/backstores> iblock/ create name=my_disk dev=/dev/sdb
Generating a wwn serial.
Created iblock storage object my_disk using /dev/sdb.
Entering new node /backstores/iblock/my_disk.
/backstores/iblock/my_disk>

targetcli automatically creates a WWN serial ID for the backstore device and then changes the working context to it.

The resulting object hierarchy looks as follows (displayed from the root object): 

/> ls
o- / ..................................................................... [...]
  o- backstores .......................................................... [...]
  | o- fileio ............................................... [0 Storage Object]
  | o- iblock ............................................... [1 Storage Object]
  | | o- my_disk .......................................... [/dev/sdb activated]
  | o- pscsi ................................................ [0 Storage Object]
  | o- rd_dr ................................................ [0 Storage Object]
  | o- rd_mcp ............................................... [0 Storage Object]
  o- ib_srpt ........................................................ [0 Target]
  o- iscsi .......................................................... [0 Target]
  o- loopback ....................................................... [0 Target]
  o- qla2xxx ........................................................ [0 Target]
/>

Alternatively, any LVM logical volume can be used as a backstore, please refer to the LIO Admin Manual on how to create them properly.

For instance, create an IBLOCK backstore on a logical volume (under /dev/<volume_group_name>/<logical_volume_name>): 

/backstores> iblock/ create name=my_disk dev=/dev/vg0/lv1
Generating a wwn serial.
Created iblock storage object my_disk using /dev/vg0/lv1.
Entering new node /backstores/iblock/my_disk.
/backstores/iblock/my_disk>

Again, targetcli automatically creates a WWN serial ID for the backstore device and then changes the working context to it.

More backstore examples
More examples on creating backstores can be found in targetcli.

Instantiate a target

Associate the three Ethernet network interfaces that are available on the storage array with FCoE via: 

echo ethX > /sys/module/fcoe/parameters/create

The three then resulting FCoE ports are presented in the WWN context with the following WWNPs:

Instantiate an FCoE target on the existing IBLOCK backstore device my_disk (as set up in targetcli): 

/backstores/iblock/my_disk> /tcm_fc create 20:00:00:0c:fc:00:f5:7b
Created target 20:00:00:0c:fc:00:f5:7b.
Entering new node /tcm_fc/20:00:00:0c:fc:00:f5:7b.
/tcm_fc/21:0...0c:fc:00:f5:7b>

targetcli automatically changes the working context to the resulting Endpoint.

Export LUNs

Declare a LUN for the backstore device, to form a valid SAN storage object: 

/tcm_fc/21:0...0c:fc:00:f5:7b> luns/ create /backstores/iblock/my_disk
Selected LUN 0.
Successfully created LUN 0.
Entering new node /tcm_fc/20:00:00:0c:fc:00:f5:7b/luns/lun0.
/tcm_fc/21:0...5:7b/luns/lun0>

targetcli automatically assigns the default ID '0' to the LUN, and then changes the working context to the SAN storage object. The LIO is now created, and exports /dev/sdb as LUN 0.

Return to the underlying Endpoint as the working context, as no attributes need to be set or modified for standard LUNs: 

/tcm_fc/21:0...5:7b/luns/lun0> cd <
Taking you back to /tcm_fc/20:00:00:0c:fc:00:f5:7b.
/tcm_fc/21:0...0c:fc:00:f5:7b>

Define access rights

Configure the access rights to allow logins from initiators. This requires setting up individual access rights for each initiators, based on its WWPN.

Determine the WWPN for the respective FCoE initiator. For instance, for Linux initiator systems, use: 

# cat /sys/class/fc_host/host*/port_name | sed -e s/0x// -e 's/../&:/g' -e s/:$//

For a simple setup, allow access to the initiator with the WWPN as determined above: 

/tcm_fc/21:0...0c:fc:00:f5:7b> acls/ create 21:00:00:24:ff:31:4c:4c
Successfully created Node ACL for 21:00:00:24:ff:31:4c:4c.
Created mapped LUN 0.
Entering new node /tcm_fc/20:00:00:0c:fc:00:f5:7b/acls/21:00:00:24:ff:31:4c:4c.
/tcm_fc/21:0...24:ff:31:4c:4c> cd /
/>

targetcli then automatically adds the appropriate mapped LUNs per default.

Display the object tree

The resulting FCoE SAN object hierarchy looks as follows (displayed from the root object): 

/> ls
o- / ..................................................................... [...]
  o- backstores .......................................................... [...]
  | o- fileio ............................................... [0 Storage Object]
  | o- iblock ............................................... [1 Storage Object]
  | | o- my_disk .......................................... [/dev/sdb activated]
  | o- pscsi ................................................ [0 Storage Object]
  | o- rd_dr ................................................ [0 Storage Object]
  | o- rd_mcp ............................................... [0 Storage Object]
  o- ib_srpt ........................................................ [0 Target]
  o- iscsi .......................................................... [0 Target]
  o- loopback ....................................................... [0 Target]
  o- qla2xxx ........................................................ [0 Target]
  o- tcm_fc ......................................................... [1 Target]
    o- 20:00:00:0c:fc:00:f5:7b ....................................... [enabled]
      o- acls .......................................................... [1 ACL]
      | o- 21:00:00:24:ff:31:4c:4c .............................. [1 Mapped LUN]
      |   o- mapped_lun0 ........................................... [lun0 (rw)]
      o- luns .......................................................... [1 LUN]
        o- lun0 .................................... [iblock/my_disk (/dev/sdb)]
/>

Persist the configuration

Don't forget to use saveconfig!
Without saveconfig, the LIO configuration will be lost upon rebooting or unloading the target service, as the target configuration will revert back to the last saved one.

Use saveconfig from the root context to persist the target configuration across LIO reboots: 

/> saveconfig
WARNING: Saving rtsnode1 current configuration to disk will overwrite your boot settings.
The current target configuration will become the default boot config.
Are you sure? Type 'yes': yes
Making backup of srpt/ConfigFS with timestamp: 2012-02-27_23:19:37.660264
Successfully updated default config /etc/target/srpt_start.sh
Making backup of qla2xxx/ConfigFS with timestamp: 2012-02-27_23:19:37.660264
Successfully updated default config /etc/target/qla2xxx_start.sh
Making backup of loopback/ConfigFS with timestamp: 2012-02-27_23:19:37.660264
Successfully updated default config /etc/target/loopback_start.sh
Making backup of LIO-Target/ConfigFS with timestamp: 2012-02-27_23:19:37.660264
Successfully updated default config /etc/target/lio_backup-2012-02-27_23:19:37.660264.sh
Making backup of Target_Core_Mod/ConfigFS with timestamp: 2012-02-27_23:19:37.660264
Successfully updated default config /etc/target/tcm_backup-2012-02-27_23:19:37.660264.sh
Generated Target_Core_Mod config: /etc/target/backup/tcm_backup-2012-02-27_23:19:37.660264.sh
Successfully updated default config /etc/target/lio_start.sh
Successfully updated default config /etc/target/tcm_start.sh
/>

Spec file

Datera spec files define the fabric-dependent feature set, capabilities and available target ports of the specific underlying fabric.

In particular, the FCoE spec file /var/target/fabric/tcm_fc.spec is included via RTSlib. WWN are extracted via /sys/class/fc_host/host*/port_name in wwn_from_files_filter, once the Ethernet device has been created with fcoe.ko, and are presented in the targetcli WWN working context to register individual FCoE port GUIDs. 

# WARNING: This is a draft specfile supplied for demo purposes only.

# The tcm_fc fabric module uses the default feature set.
features = acls

# Non-standard module naming scheme
kernel_module = tcm_fc

# The module uses hardware addresses from there
wwn_from_files = /sys/class/fc_host/host*/port_name

# Transform '0x1234567812345678' WWN notation to '12:34:56:78:12:34:56:78'
wwn_from_files_filter = "sed -e s/0x// -e 's/../&:/g' -e s/:$//"

# The configfs group is default
configfs_group = fc

Specifications

The full advanced LIO SPC-3/SPC-4 SCSI logic (such as PRs, ALUA, VAAI, etc.) is inherently working on FCoE Ports and (across) all other fabric modules, such as FCoE, Fibre Channel, iSCSI, iSER, vHost, etc.

The following specifications are available from the T11 Working Group:

Acknowledgements

FCoE was made possible by Joe Eykholt's generous contributions to tcm_fc, and his ongoing work of making the Linux libfc target capable.

See also

Notes

  1. ↑ Linus Torvalds (2011-07-21). "Linux 3.0". lkml.org. 

External links

Timeline of the LinuxIO
Release Details 2011 2012 2013 2014 2015
123456789101112 123456789101112 123456789101112 123456789101112 123456789101112
4.x Version 4.0 4.1
Feature LIO Core Loop back FCoE iSCSI Perf SRP
 		CM WQ FC
USB
1394 		vHost Perf Misc 16 GFC iSER Misc VAAI Misc DIF Core
NPIV 		DIF iSER DIF FC vhost TCMU Xen Misc Misc virtio 1.0 Misc NVMe OF
Linux 2.6.38 2.6.39 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 3.20 3.21 3.22
Retrieved from "http://www.linux-iscsi.org/wiki/Fibre_Channel_over_Ethernet"
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