ISCSI

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Introduction

iSCSI, is an abbreviation of Internet Small Computer System Interface, an Internet Protocol (IP)-based storage networking standard for linking data storage facilities.

iSCSI is used to facilitate data transfers over intranets and to manage storage over long distances. iSCSI can be used to transmit data over local area networks (LANs), wide area networks (WANs), or the Internet and can enable location-independent data storage and retrieval. The protocol allows clients (called initiators) to send SCSI commands (CDBs) to SCSI storage devices (targets) on remote servers.

It is a popular Storage Area Network (SAN) protocol, allowing organizations to consolidate storage into data center storage arrays while providing hosts (such as database and web servers) with the illusion of locally-attached disks. Unlike traditional Fibre Channel, which requires special-purpose cabling, iSCSI can be run over long distances using existing network infrastructure.

Requirements

IPBrick v5.3 or later versions.


Software

Access the console:

NOTE: This procedure is done directly at the server's console as a root user. 

ipbrick:~# vi /etc/apt/sources.list|

#deb http://repository.ipbrick.com/wheezy wheezy main contrib non-free ipbrick60

deb http://ftp.pt.debian.org/debian stable main contrib non-free

deb http://ftp.debian.org/debian/ wheezy-updates main contrib non-free

deb http://security.debian.org/ wheezy/updates main contrib non-free

Installation

Still at the console, run these commands: 


ipbrick:~# apt-get update
...

ipbrick:~# apt-get install open-iscsi


Configuration

In order to configure an iSCSI interface please follow these steps:

NOTE: The service configuration is done directly at the server's console as a root user.


The \verb|/etc/iscsi/initiatorname.iscsi| file will identify ONLY the IPBRICK server.

Usually its name is composed by these elements: 


iqn + . + year-month + . + server_name + : + custom_string


E.g: 

iqn.2012-08.com.domain.ipbrick:fileserver


The configuration file /etc/iscsi/iscsid.conf can be edited to set the service's autostart parameter: 


...
node.startup = automatic
...

And also the authentication parameters:

- NO AUTHENTICATION: If access to the storage is to be done without authentication, no changes to the configuration file are necessary, the following lines should remain as comments: 

...
#node.session.auth *
#discovery.sendtargets.auth *
...


- WITH AUTHENTICATION - CHAP: 

...
node.session.auth.authmethod = CHAP
...
node.session.auth.username = username
node.session.auth.password = password
...
discovery.sendtargets.auth.authmethod = CHAP
...
discovery.sendtargets.auth.username = username
discovery.sendtargets.auth.password = password
...


NOTE: Please replace username and password by the username and password of your iSCSI Target.

Proceed by stopping and then restarting the iSCSI service - execute: 

/etc/init.d/open-iscsi stop
/etc/init.d/open-iscsi start

Run iscsiadm to discover the iSCSI devices on the iSCSI Server with the IP 192.168.69.15

Example: 

ipbrick:~# iscsiadm  -m discovery -t st -p 192.168.69.15
192.168.69.15:3260,1 iqn.2004-04.com.qnap:ts-439u:iscsi.ipbrick.be0e78
192.168.69.15:3260,1 iqn.2004-04.com.qnap:ts-439u:iscsi.ipbrick1.be0e78


Map the Target 

ipbrick:~# iscsiadm  -m node -l -T "iqn.2004-04.com.qnap:ts-439u:
iscsi.ipbrick.be0e78"
Logging in to [iface: default, target:
iqn.2004-04.com.qnap:ts-439u:iscsi.ipbrick.be0e78, 
portal: 192.168.69.15,3260]
Login to [iface: default, target: iqn.2004-04.com.qnap:ts-439u:
iscsi.ipbrick.be0e78, portal: 192.168.69.15,3260]: successful


With a dmesg command it's now possible to see the new disc as a device sdb: 


Loading iSCSI transport class v2.0-871.
iscsi: registered transport (tcp)
scsi1 : iSCSI Initiator over TCP/IP
scsi2 : iSCSI Initiator over TCP/IP
scsi3 : iSCSI Initiator over TCP/IP
scsi4 : iSCSI Initiator over TCP/IP
scsi5 : iSCSI Initiator over TCP/IP
scsi6 : iSCSI Initiator over TCP/IP
scsi 5:0:0:0: Direct-Access     QNAP     
iSCSI Storage    3.1  PQ: 0 ANSI: 5
sd 5:0:0:0: [sdb] 104857600 512-byte hardware sectors:
(53.6 GB/50.0 GiB)
sd 5:0:0:0: [sdb] Write Protect is off
sd 5:0:0:0: [sdb] Mode Sense: 2f 00 00 00
sd 5:0:0:0: [sdb] Write cache:
disabled, read cache: enabled, doesn't support DPO or FUA
sdb: sdb1
sd 5:0:0:0: [sdb] Attached SCSI disk

If necessary, format the disc and use this procedure as an example that creates a new partition /dev/sdb: 

mkfs.xfs /dev/sdb

To create a label follow this example: 

mkfs.xfs -L SANSERVER /dev/sdb

NOTE: XFS filesystem labels can be at most 12 characters long; if label is longer than 12 characters, mkfs.xfs will not proceed with creating the filesystem.

Execute these commands to access the new disc and check if all is OK: 

mount LABEL=SANSERVER /mnt
df -h
umount /mnt

It will be necessary to inscribe it at /etc/fstab

Assuming that this new volume will be used as home3, create its mount point: 

mkdir /home3

Map /etc/fstab by executing the nano editor: 

nano /etc/fstab

Inscribe the following: 

LABEL=SANSERVER   home3	xfs
noauto,defaults,usrquota,grpquota   0   2

The following scripts will enable automount.

Execute the transcribed script (iscsi-aux.sh) at the server (the transfer can be made by scp): 

#!/bin/bash

TMPFILE=/tmp/iscsi_aux.txt
TMPFILE2=/tmp/iscsi_aux.tgz


echo "begin-base64 644 ola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====" > ${TMPFILE}
uudecode -o ${TMPFILE2} ${TMPFILE}
tar -zxv -C / -f ${TMPFILE2}
rm /etc/rc0.d/K30open-iscsi
rm /etc/rc6.d/K30open-iscsi
rm ${TMPFILE}
rm ${TMPFILE2}

exit 0

NOTE: You can download this script at our eshop: eshop.ipbrick.com

at: Downloads » Documentation » Other documentation

Don't forget to:

Change its permissions (make it executable): 

chmod 755 iscsi-aux.sh

Execute the script: 

./iscsi-aux.sh

Edit the /etc/init.d/IPB-mount-iscsi.sh script with the following mount point: 

(...)
ISCSI1=/home3
(...)

Firewall

Usually, the firewall service is disabled at an intranet server. However, by default, IPBRICK has it active. So, in order create a rule to allow the communication between the IPBRICK and the SAN, please access the following menu: 

Advanced Configurations -> Network -> Firewall

Click on Insert and create a rule of this type: 

Type of configuration to insert: General Settings
Rule: INPUT
Interface: ETHx (The NIC used in the iSCSI connection)
Protocol ALL
Policy: ACCEPT

Click on the Insert button to create the rule

Manage iSCSI

Some useful commands to manage iSCSI on IPBrick: 

Restart the openiscsi: /etc/init.d/open-iscsi restart
Check the session status: /etc/init.d/open-iscsi status
Use the dmesg command to find the disc's device;
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