Deep dive into iSCSI

INTRODUCTION

iSCSI stands for Internet small computer system interface. It is a storage area network protocol used to send block storage from storage arrays or devices to client computer that directly connected to  those devices..

An iSCSI storage area network consist of iSCSI target on storage array controllers & iSCSI initiator on storage clients. This storage and array controller are used by iSCSI protocol to connect storage to clients & are represented by unique name called iSCSI Qaulified name (IQN).

Computer os can include or can be installed by iSCSI initiators where some storage are designed to provide only storage our iSCSI many storage come equiped with iSCSI target in addition to other common protocol ( Fiber channel, Fiber channel our ethernet, SMB).

iSCSI Advantages

1) Single network for SAN & LAN.

2) Inexpensive traditional ethernet network.

3) iSCSI knows no limits in terms of distance as long as there is network connectivity.

4) iSCSI  provides SAN for all kinds of machines from desktops to high end servers.

5) iSCSI SAN environments can be easily deployed by leveraging existing network hardware and other components.

iSCSI Terminology

1) iqn: iSCSI Qualified name

    iqn format: iqn.yyyy-mm.com.reverse_domain_name:optional string

    eg. iqn.2016-10.com.example:storage

2) Target: Storage resource made available by iSCSI server.

3) LUN: Logical unit number, Numbered block devices.

Configuring iSCSI Storage

1) On iSCSI Target server side.

  i)  Before going to create iSCSI target we will create LVM partition that we are going to use for iSCSI target.

   I am attaching screens for easy understanding of partition creation:

     We have to  create LVM partition so need to select partition type LVM as shown bellow:

  

   As shown in above screen we have created LVM partition of 4GB in volume group iscsi.

  ii)    On iSCSI Target server we will create Target i.e iSCSI storage using bellow steps:
    targetcli is the package needed to create and configure  iSCSI storage luns in Linux.

After entering cd  on command prompt it will show all locations present as bellow screen:

Select backstore from the available locations list:

We will get bellow screen after hitting cd which will show all configuration on target server.

Last step is to adding service in firewalld:

This completes configuration on Target server.


2) On iSCSI Client side.

    Client side we have to install iSCSI initiator for initiating connection with target server.

Next step is to discover iSCSI partitions from target server.

 Above command will discover iSCSI target from target server. (IP is of the target server)

 No need to remember above command you will get this command from man page of iscsiadm examples section. Just copy that command and  replace ip of the target server.

Once we discover target server. We need to add target server iqn into client system iSCSI initiator name. 

After discovering target next step we have to attached that target to client system as follows:

You will get above command from man page of iscsiadm 2nd example. Just copy and replace target name and IP of the target server. Once, you see listing of iSCSI target from lsscsi command create partition using fdisk or parted and format the partition with desire filesystem as you required. Add the entry of partition in /etc/fstab file. After that you will able to use iSCSI partition as locally mounted partition. You will not see any difference between iscsi partition and local partition.