iSCSI stands for Small Computer System Interface (SCSI) over IP. SCSI in a nutshell is set of commands, protocols and standards for transferring data between peripheral devices. Using iSCSI we can set storage to a remote machine using reliable protocols and methods.

The configure iSCSI you have to configure the following components:

• iSCSI Target - This is the server which will receive the data: Receiver
  • With a LUN (the storage location)
• iSCSI Initiator - This is the server which will send the data: Sender

So let's get going :)

The iSCSI target is usually configured via wizard or manually, that depends on the server. I will not go into details here but here is a picture of how it is configured on ASUSTORE NAS - AS202TE

It is important to note, that the iSCSI target is just the pointer to the LUN (Logical Unit Number).

So the connection will be initiated by the iSCSI initiator (on the client machine) → iSCSI Target (on the server machine, over Internet) → LUN (at the storage level)

iSCSI initiator again depends on the operation system on the server.

Windows has integrated iSCSI initiator when you are installing it. Hopefully you have something higher than Windows 98 :). The wizzard is pretty straight forward, you have to specify the iSCSI target server and it will discover the targets for you. Then you can just connect and map the device. Given no authentication is required.

The configuration for windows is so trivial via the wizard that I don't think I should even discuss it.

On linux the situation is a little bit different. By default Linux doesn't install the initiator, so you have to install it yourself. Furthermore, like anything, there isn't GUI so you have to configure it yourself manually.

[root@matar ~]# yum install iscsi-initiator-utils -y
Loaded plugins: langpacks, product-id, search-disabled-repos, subscription-manager
This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register.
Nothing to do
[root@matar ~]# yum list | grep iscsi
iscsi-initiator-utils.x86_64             6.2.0.873-32.el7          @anaconda/7.2  <- Already installed 
iscsi-initiator-utils-iscsiuio.x86_64    6.2.0.873-32.el7          @anaconda/7.2  
libiscsi.x86_64                          1.9.0-6.el7               @anaconda/7.2
netbsd-iscsi.x86_64                      20080207-9.el7            epel

You have new mail in /var/spool/mail/root

To discover the targets we can issue the following command:

[root@clientserver ~]# iscsiadm -m discovery -t st -p 10.200.15.30
iscsi_target_server_ip:3260,1 iqn.1991-05.com.microsoft:taurus-taurus-orabackup-target
You have mail in /var/spool/mail/root

This will show us the exposed iSCSI targets. In our case we have iscsi target which is on port: 3260 and with name: “iqn.1991-05.com.microsoft:taurus-taurus-orabackup-target”