Advancelinux.blogspot.in 2012 02 Configuring on Rhel 6 i

7/28/2019 Advancelinux.blogspot.in 2012 02 Configuring on Rhel 6 i

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Configuring iSCSI target on RHEL 6

Introduction:

iSCSI is Internet SCSI (Small Computer System Interface), an Internet Protocol (IP)-

based storage networking standard for linking data storage facilities by carrying SCSI

commands over IP networks. iSCSI is used to facilitate data transfers over intranets and

to manage storage over long distances. iSCSI makes block devices available via the

network. We can mount block devices (disks) across an IP network to local system and

then use them like any other block device. iSCSI is a client-server protocol. The server-

side is referred to as the 'target,' while the client-side is referred to as the 'initiator.' Both

the target and initiator are uniquely identified by a string called the iSCSI Qualified Name

(iQN). Initiators come in two varieties: software and hardware. A software initiator is just

a driver that handles all requests and pairs the network interfaces driver and the SCSI

drivers together to make it work. Using a software initiator any system with an Ethernetcard can act as an iSCSI initiator. A hardware initiator is an iSCSI HBA, which is basically

just an ethernet card with a SCSI ASIC onboard. Here we are configuring software

initiator in RHEL 6.

OS installation:

Install RHEL 6 on the server with basic server installation and configure yum server on

the machine.

Network setup:

Configure network with ipaddress and make sure that clients are reachable to the server.

By default iSCSI will listen to the port 3260, we have to add necessary rules in iptables to

allow iSCSI. I gnore this step if firewall is disabled.

# iptables -I INPUT -p tcp -m tcp --dport 3260 -j ACCEPT

# service iptables save

# service iptables restart

Install and enable the iSCSI target service:

Install and enable the iSCSI target service with the following commands

# yum install scsi-target-utils

# chkconfig tgtd on

# service tgtd start

Allocate storage for the LUNs:

The iSCSI target service is not dependent on a particular type of exported LUN. The LUNs

can be plain files, LVM volumes, or block devices. There is however a performance

overhead if using the LVM and/or file system layers as compared to block devices. This

example demonstrates the creationof a local partition /dec/sdc1 as iSCSI storage LUN

iSCSI server configuration in RHEL6

Page 1 of 5iSCSI server configuration in RHEL6

4/19/2013http://advancelinux.blogspot.in/2012/02/configuring-on-rhel-6-introduction.html


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# fdisk -l /dev/sdc

Di sk / dev/ sdc: 3221 MB, 3221225472 bytes

255 heads, 63 sector s/ t r ack, 391 cyl i nder s

Uni t s = cyl i nders of 16065 * 512 = 8225280 byt es

Sector si ze ( l ogi cal / physi cal ) : 512 bytes / 512 bytes

I / O si ze (mi ni mum/ opt i mal ) : 512 byt es / 512 byt es

Di sk i dent i f i er : 0xc9a1606e

Devi ce Boot St ar t End Bl ocks I d

Syst em

/ dev/ sdc1 1 391 3140676 83

Li nux

Create the targets:

Targets can be created by adding an XML entry to the /etc/tgt/targets.conffile,

using text editor. Following entries to be added.

#vi /etc/tgt/targets.confdef aul t - dr i ver i scsi

backi ng- st or e / dev/ sdc1

wr i t e- cache of f

Note:

The target attribute requires an iSCSI Qualified Name (IQN),following is the general

format:

iqn.yyyy-mm.reversed.domain.name:OptionalIdentifierText

yyyy-mm represents the 4-digit year and 2-digit month the device was started (for

example: 2011-07)

reversed.domain.name is the hosts domain name in reverse. For example,

server1.example.com, in an IQN, becomes com.example.server1;

OptionalIdentifierText is any text string, without spaces, that helps the administrator

identifies which device.

Restart tgtd service:

Need to restart tgtd service after configuring iscsi target

# service tgtd restart

St oppi ng SCSI t arget

daemon: [ OK ]

St ar t i ng SCSI t ar get

daemon: [ OK ]

Checking configuration:

To confirm the successful operation , query the iSCSI target setup using following

command




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# tgt-admin --show

Target 1: i qn. 2008- 09. com. exampl e: ser ver . t ar get 1

System i nf ormati on:

Dr i ver : i scs i

St ate: r eady

I _T nexus i nf ormat i on:

LUN i nf ormat i on:

LUN: 0

Type: cont r ol l er

SCSI I D: I ET 00010000

SCSI SN: beaf 10

Si ze: 0 MB

Onl i ne: Yes

Removabl e medi a: No

Backi ng st ore t ype: r dwr

Backi ng st ore path: None

LUN: 1

Type: di sk

SCSI I D: I ET 00010001

SCSI SN: beaf 11

Si ze: 3216 MB

Onl i ne: Yes

Removabl e medi a: No

Backi ng st ore t ype: r dwr

Backi ng st ore pat h: / dev/ sdc1

Account i nf ormat i on:

ACL i nf ormat i on:

ALL

Client side configuration:

1 ) Install iscsi-initiator-utils package on the client using yum

# yum install iscsi-initiator-utils

2 )Discover the target LUNs exported by server using following command. It will provide

iqn name with of LUN associated with given ip address

# iscsiadm -m discovery -t sendtargets -p 10.30.32.206

Star t i ng i scs i d:

[ OK ]

10. 30. 32. 206: 3260, 1 i qn. 2008-

09. com. exampl e: server . t ar get 1t

Note :

-p : it is indicates the address of target server.

3) To connect iSCSI target we can use following command , we need to mention server

ip and iqn name.

# iscsiadm -m node -T iqn.2008-09.com.example:server.target1 p

10.30.32.206 login




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Note :

-p : it is indicates the address of target server.

-T : This option specifies iqn of target server

Now iSCSI target is connected from ip 10.30.32.206.To find out the device associated

with the iSCSI LUN. We have to check /var/log/message

# tail /var/log/messagesDec 26 14: 22: 50 l ocal host ker nel : scsi 3: 0: 0: 0: At t ached scsi

gener i c sg4 t ype 12

Dec 26 14: 22: 50 l ocal host ker nel : scsi 3: 0: 0: 1: Di r ect- Access

I ET VI RTUAL- DI SK 0001 PQ: 0 ANSI : 5

Dec 26 14: 22: 50 l ocal host ker nel : sd 3: 0: 0: 1: At t ached scsi

generi c sg5 t ype 0

Dec 26 14: 22: 50 l ocal host kernel : sd 3: 0: 0: 1: [ sdd] 6281352 512-

byte l ogi cal bl ocks: ( 3. 21 GB/ 2. 99 Gi B)

Dec 26 14: 22: 50 l ocal host ker nel : sd 3: 0: 0: 1: [ sdd] Wr i t e Pr ot ect

i s of f

Dec 26 14: 22: 50 l ocal host kernel : sd 3: 0: 0: 1: [ sdd] Wr i t e cache:di sabl ed, r ead cache: enabl ed, doesn' t suppor t DPO or FUA

Dec 26 14:22:50 localhost kernel: sdd: sdd1

Dec 26 14: 22: 50 l ocal host ker nel : sd 3: 0: 0: 1: [ sdd] At t ached SCSI

di sk

Dec 26 14: 22: 50 l ocal host l i bvi r t d: 14: 22: 50. 833: er r or :

udevGetSCSI Type: 747 : Fai l ed t o f i nd SCSI devi ce t ype 12

Dec 26 14: 22: 50 l ocal host i scsi d: Connect i on1: 0 t o [ t ar get :

i qn. 2008- 09. com. exampl e: server. t arget 1, port al : 10. 30. 32. 206, 3260]

t hr ough [ i f ace: def aul t ] i s oper at i onal now

In this demo, iSCSI LUN is linked as/ ded/ sdd1

Creating file system:

we can create file system on /ded/sdd1 and use locally.

# mkfs.ext3 /dev/sdd1

# mkdir iSCSI

# mount /dev/sdd1 /iSCSI/

Adding entry in /etc/fstab:

Find out UUID of device using following command

# blkid /dev/sdd1/ dev/ sdd1: UUI D="9674832d- c995- 4ac8- b6da-0d25ef a088d0" TYPE="ext 3"

Add the following entry in/et c/ fst abusing vi editor.

UUID= 9674832d-c995-4ac8-b6da-0d25efa088d0 /iSCSI ext3 _netdev 0 0

[ r oot @dhcpserver / ] #cat /etc/fstab

#

# / et c / f st ab




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# Cr eated by anaconda on Thu J un 2 00: 41: 38 2011

#

# Accessi bl e f i l esyst ems, by ref er ence, ar e mai nt ai ned under

' / dev/ di sk'

# See man pages f st ab( 5) , f i ndf s( 8) , mount ( 8) and/ or bl ki d( 8) f or

more i nf o

#

/ dev/ mapper / Vol Gr oup- l v_root / ext 4

def aul t s 1 1

UUI D=9c732237- b39f - 4024- a631- 3c264e637179 / boot

ext4 def aul t s 1 2

/ dev/ mapper / Vol Gr oup- l v_swap swap swap

def aul t s 0 0

t mpf s / dev/ shm t mpf s

def aul t s 0 0

devpt s / dev/ pt s devpt s

gi d=5, mode=620 0 0

sysf s / sys sysf s

def aul t s 0 0

pr oc / pr oc pr oc

def aul t s 0 0

UUID=9674832d-c995-4ac8-b6da-0d25efa088d0 /iSCSI ext3

_netdev 0 0

The added entry is highlighted in the above output.

Note:

We must use_netdevparameter while adding entry in /etc/fstab,Which is

used to prevent the system from attempting to mount the file systems until thenetwork has been enabled on the system.


4/19/2013h // d li bl i /2012/02/ fi i h l 6 i d i h l

Advancelinux.blogspot.in 2012 02 Configuring on Rhel 6 i

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