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https://github.com/SCST-project/scst.git
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Gleb Chesnokov
be60953eb1
The FCST setup has stale step references and an invalid target enable path. A reader following it reaches the wrong prerequisites and cannot address enabled after entering the target directory. Commit87bde8ab0e("fcst/README: Update this README file") shortened the procedure without updating its cross-references. Commit7a12737c9d("Simplify README by eliminating example using of ini_groups.") changed the LUN setup but left $LPORT duplicated in the following path. Repair the references, terminology and relative enable command, and clarify the LUN 0 compatibility note. The same procedure installs packages, creates an FCoE interface, loads modules and exports storage, so require authorization for the host, CNA, fabric, initiators and backing devices before it is run.
About fcst
==========
The fcst kernel module implements an SCST target driver for the FCoE protocol.
FCoE or Fibre Channel over Ethernet is a protocol that allows to communicate
fibre channel frames over an Ethernet network. Since the FCoE protocol
requires a lossless Ethernet network, special network adapters and switches
are required. Ethernet network adapters that support FCoE are called
Converged Network Adapters (CNA). The standard that makes lossless Ethernet
communication possible is called DCB or Data Center Bridging.
Since FCoE frames are a kind of Ethernet frames, communication between FCoE
clients and servers is limited to a single Ethernet broadcast domain.
Building and Installing
=======================
FCST is a kernel module that depends on libfc and SCST to provide FC target
support.
WARNING: The procedure below installs system packages, creates an FCoE
interface, loads kernel modules, changes live SCST sysfs state, exposes LUNs,
and may reset an initiator interface. Use it only with authorization for the
exact host, Ethernet fabric, CNA, initiators, and backing storage. Substitute
and verify every interface name, port name, and SCST device before running a
command.
1. Build and install scst, fcst and scstadmin following the instructions
in the top-level INSTALL.md file.
2. Install the FCoE admin tools:
apt-get install fcoe-utils lldpad ||
dnf install fcoe-utils lldpad ||
zypper install fcoe-utils open-lldp
3. Bring up SCST and configure the devices.
4. Bring up an FCoE initiator (we'll enable target mode on it later):
modprobe fcoe
fcoeadm -c eth3
The other end can be an initiator as well, in point-to-point mode
over a full-duplex loss-less link (enable pause on both sides).
Alternatively, the other end can be an FCoE switch.
5. Use fcc from the open-fcoe contrib tools to inspect the initiator
setup and obtain the FCoE port name for eth3:
# fcc
FC HBAs:
HBA Port Name Port ID State Device
host4 20:00:00:1b:21:06:58:21 01:01:02 Online eth3
host4 Remote Ports:
Path Port Name Port ID State Roles
4:0-0 10:00:50:41:4c:4f:3b:00 01:01:01 Online FCP Initiator
In the above example, there's one local host on eth3, and it's in
a point-to-point connection with the remote initiator with Port_id 010101.
6. Load fcst
modprobe fcst
7. Add the SCST devices configured in step 3 that you want to export.
Many initiators require a LUN 0.
LPORT=20:00:00:1b:21:06:58:21 # the local Port_Name
cd /sys/kernel/scst_tgt/targets/fcst/$LPORT
echo add disk-name 0 > luns/mgmt
echo add disk-name 1 > luns/mgmt
8. Enable the target:
echo 1 > enabled
9. As a temporary workaround, you may need to reset the interface
on the initiator side so it sees the SCST device as a target and
discovers LUNs. You can avoid this by bringing up the initiator last.