Internet SCSI (iSCSI) is a network protocol s that allows you to use of the SCSI protocol over TCP/IP networks. It is good alternative to Fibre Channel-based SANs. You can easily manage, mount and format iSCSI Volume under Linux. It allows access to SAN storage over Ethernet.
Open-iSCSI project is a high-performance, transport independent, multi-platform implementation of iSCSI. Open-iSCSI is partitioned into user and kernel parts.
Instructions are tested on:
[a] RHEL 5
[b] CentOS 5
[c] Fedora 7
[d] Debian / Ubuntu Linux
iscsi-initiator-utils RPM package — The iscsi package provides the server daemon for the iSCSI protocol, as well as the utility programs used to manage it. iSCSI is a protocol for distributed disk access using SCSI commands sent over Internet Protocol networks. This package is available under Redhat Enterprise Linux / CentOS / Fedora Linux and can be installed using yum command:
# yum install iscsi-initiator-utils
If you are using Debian / Ubuntu Linux install open-iscsi package, enter:
$ sudo apt-get install open-iscsi
There are three steps needed to set up a system to use iSCSI storage:
Open /etc/iscsi/iscsid.conf with vi text editor:
# vi /etc/iscsi/iscsid.conf
Setup username and password:
node.session.auth.username = My_ISCSI_USR_NAME
node.session.auth.password = MyPassword
discovery.sendtargets.auth.username = My_ISCSI_USR_NAME
discovery.sendtargets.auth.password = MyPassword
Where,
You may also need to tweak and set other options. Refer to man page for more information. Now start the iscsi service:
# /etc/init.d/iscsi start
Now use iscsiadm command, which is a command-line tool allowing discovery and login to iSCSI targets, as well as access and management of the open-iscsi database. If your storage server IP address is 192.168.1.5, enter:
# iscsiadm -m discovery -t sendtargets -p 192.168.1.5
# /etc/init.d/iscsi restart
Now there should be a block device under /dev directory. To obtain new device name, type:
# fdisk -l
or
# tail -f /var/log/messages
Output:
Oct 10 12:42:20 ora9is2 kernel: Vendor: EQLOGIC Model: 100E-00 Rev: 3.2 Oct 10 12:42:20 ora9is2 kernel: Type: Direct-Access ANSI SCSI revision: 05 Oct 10 12:42:20 ora9is2 kernel: SCSI device sdd: 41963520 512-byte hdwr sectors (21485 MB) Oct 10 12:42:20 ora9is2 kernel: sdd: Write Protect is off Oct 10 12:42:20 ora9is2 kernel: SCSI device sdd: drive cache: write through Oct 10 12:42:20 ora9is2 kernel: SCSI device sdd: 41963520 512-byte hdwr sectors (21485 MB) Oct 10 12:42:20 ora9is2 kernel: sdd: Write Protect is off Oct 10 12:42:20 ora9is2 kernel: SCSI device sdd: drive cache: write through Oct 10 12:42:20 ora9is2 kernel: sdd: unknown partition table Oct 10 12:42:20 ora9is2 kernel: sd 3:0:0:0: Attached scsi disk sdd Oct 10 12:42:20 ora9is2 kernel: sd 3:0:0:0: Attached scsi generic sg3 type 0 Oct 10 12:42:20 ora9is2 kernel: rtc: lost some interrupts at 2048Hz. Oct 10 12:42:20 ora9is2 iscsid: connection0:0 is operational now
/dev/sdd is my new block device.
You can now partition and create a filesystem on the target using usual fdisk and mkfs.ext3 commands:
# fdisk /dev/sdd
# mke2fs -j -m 0 -O dir_index /dev/sdd1
OR
# mkfs.ext3 /dev/sdd1
Tip: If your volume is large size like 1TB, run mkfs.ext3 in background using nohup:
# nohup mkfs.ext3 /dev/sdd1 &
Mount new partition:
# mkdir /mnt/iscsi
# mount /dev/sdd1 /mnt/iscsi
First make sure iscsi service turned on at boot time:
# chkconfig iscsi on
Open /etc/fstab file and append config directive:
/dev/sdd1 /mnt/iscsi ext3 _netdev 0 0
Save and close the file.