iscsi storage is used as shared storage in Redhat cluster, VMware vsphere, Redhat Enterprise Virtualization Manager, Ovirt, etc.

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1 Configure iscsi Target & Initiator on CentOS 7 / RHEL7 iscsi stands for Internet Small Computer Systems Interface, IP-based storage, works on top of internet protocol by carrying SCSI commands over IP network. iscsi transports block-level data between an iscsi initiator on a client machine and an iscsi target on a storage device (server). iscsi storage is used as shared storage in Redhat cluster, VMware vsphere, Redhat Enterprise Virtualization Manager, Ovirt, etc. Environment Server: server.itzgeek.local IP Address: OS: CentOS Linux release (Core) Client: node1.itzgeek.local IP Address: OS: CentOS Linux release (Core) Storage Configuration Here, we will create 5GB of LVM disk on the target server to use as shared storage for clients. Let s list the available disks attached to the target server using below command. If you want to use the whole disk for LVM, then skip the disk partitioning step. [root@server ~]# fdisk -l grep -i sd Disk /dev/sda: GB, bytes, sectors

2 /dev/sda1 * Linux /dev/sda e Linux LVM Disk /dev/sdb: 10.7 GB, bytes, sectors From the above output, you can see that my system has a 10GB of disk (/dev/sdb). We will create a 5GB partition on the above disk and will use it for LVM. [root@server ~]# fdisk /dev/sdb Welcome to fdisk (util-linux ). Changes will remain in memory only, until you decide to write them. Be careful before using the write command. Device does not contain a recognized partition table Building a new DOS disklabel with disk identifier 0x173dfa4d. Command (m for help): n --> New partition Partition type: p primary (0 primary, 0 extended, 4 free) e extended Select (default p): p --> Pimary partition Partition number (1-4, default 1): 1 - -> Partition number First sector ( , default 2048): --> Just enter Using default value 2048 Last sector, +sectors or +size{k,m,g} ( , default ): +5G --> Enter the size Partition 1 of type Linux and of size 5 GiB is set Command (m for help): t --> Change label Selected partition 1 Hex code (type L to list all codes): 8e --> Change it as LVM label Changed type of partition 'Linux' to 'Linux LVM' Command (m for help): w --> Save The partition table has been altered! Calling ioctl() to re-read partition table. Syncing disks. Create a LVM with /dev/sdb1 partition (replace /dev/sdb1 with your disk name) [root@server ~]# pvcreate /dev/sdb1 [root@server ~]# vgcreate vg_iscsi /dev/sdb1 [root@server ~]# lvcreate -l 100%FREE -n lv_iscsi vg_iscsi

3 Configure iscsi target Now you have an option of creating target either with or without authentication. In this article, you can find steps for both scenarios. It is up to you to decide which one is suitable for your environment. Here, will configure iscsi target without CHAP authentication. Install the targetcli package on the server. ~]# yum install targetcli -y Once you installed the package, enter below command to get an iscsi CLI for an interactive prompt. ~]# targetcli Warning: Could not load preferences file /root/.targetcli/prefs.bin. targetcli shell version 2.1.fb41 Copyright by Datera, Inc and others. For help on commands, type 'help'. > Now use an existing logical volume (/dev/vg_iscsi/lv_iscsi) as a block-type backing store for storage object scsi_disk1_server. /> cd backstores/block /backstores/block> create scsi_disk1_server /dev/vg_iscsi/lv_iscsi Created block storage object scsi_disk1_server using /dev/vg_iscsi/lv_iscsi. Create a target. /backstores/block> cd /iscsi /iscsi> create iqn local.itzgeek.server:disk1 Created target iqn local.itzgeek.server:disk1. Created TPG 1. Global pref auto_add_default_portal=true Created default portal listening on all IPs ( ), port /iscsi> Create ACL for client machine (It s the IQN which clients use to connect).

4 /iscsi> cd /iscsi/iqn local.itzgeek.server:disk1/tpg1/acls /iscsi/iqn.20...sk1/tpg1/acls> create iqn local.itzgeek.server:node1node2 Created Node ACL for iqn local.itzgeek.server:node1node2 Create a LUN under the target. The LUN should use the previously mentioned backing storage object named scsi_disk1_server. /iscsi/iqn.20...er:disk1/tpg1> cd /iscsi/iqn local.itzgeek.server:disk1/tpg1/luns /iscsi/iqn.20...sk1/tpg1/luns> create /backstores/block/scsi_disk1_server Created LUN 0. Created LUN 0->0 mapping in node ACL iqn local.itzgeek.server:node1node2 Verify the target server configuration. /iscsi/iqn.20.../tpg1/portals> cd / /> ls o- / [...] o- backstores [...] o- block... [Storage Objects: 1] o- scsi_disk1_server... [/dev/vg_iscsi/lv_iscsi (5.0GiB) write-thru activated] o- fileio... [Storage Objects: 0] o- pscsi... [Storage Objects: 0] o- ramdisk... [Storage Objects: 0] o- iscsi... [ Targets: 1] o- iqn local.itzgeek.server:disk1.... [TPGs: 1] o- tpg1... [gen-acl s, no-auth] o- acls.... [ACLs: 1]

5 o- iqn local.itzgeek.server:node1node2... [Mapp ed LUNs: 1] o- mapped_lun0... [lun0 block/scsi_disk1_s erver (rw)] o- luns.... [LUNs: 1] o- lun0... [block/scsi_disk1_server (/dev/vg_iscsi /lv_iscsi)] o- portals... [ Portals: 1] o : [OK] o- loopback... [ Targets: 0]Save and exit from target CLI. /> saveconfig Last 10 configs saved in /etc/target/backup. Configuration saved to /etc/target/saveconfig.json /> exit Global pref auto_save_on_exit=true Last 10 configs saved in /etc/target/backup. Configuration saved to /etc/target/saveconfig.json Enable and restart the target service. [root@server ~]# systemctl enable target.service [root@server ~]# systemctl restart target.service Configure the firewall to allow iscsi traffic. [root@server ~]# firewall-cmd --permanent --add-port=3260/tcp [root@server ~]# firewall-cmd --reload

6 Configure Initiator Now, it s the time to configure a client machine to use the created target as storage. Install the below package on the client machine (node1). [root@node1 ~]# yum install iscsi-initiator-utils -y Edit the initiatorname.iscsi file. [root@node1 ~]# vi /etc/iscsi/initiatorname.iscsi Add the iscsi initiator name. InitiatorName=iqn local.itzgeek.server:node1node2 Discover the target using the below command. [root@node1 ~]# iscsiadm -m discovery -t st -p :3260,1 iqn local.itzgeek.server:disk1 Restart and enable the initiator service. [root@node1 ~]# systemctl restart iscsid.service [root@node1 ~]# systemctl enable iscsid.service Login to the discovered target. [root@node1 ~]# iscsiadm -m node -T iqn local.itzgeek.server:disk1 -p l Logging in to [iface: default, target: iqn local.itzgeek.server:disk1, portal: ,3260] (multiple) Login to [iface: default, target: iqn local.itzgeek.server:disk1, portal: ,3260] successful.

7 Create File System on ISCSI Disk After login (connecting) to discovered target, have a look at messages file. You would find similar output like below, from where you can find a name of the disk. [root@node1 ~]# cat /var/log/messages Feb 23 14:54:47 node2 kernel: sd 34:0:0:0: [sdb] byte logical blocks: (5.36 GB/4.99 GiB) Feb 23 14:54:47 node2 kernel: sd 34:0:0:0: [sdb] Write Protect is off Feb 23 14:54:47 node2 kernel: sd 34:0:0:0: [sdb] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA Feb 23 14:54:48 node2 kernel: sdb: unknown partition table Feb 23 14:54:48 node2 kernel: sd 34:0:0:0: [sdb] Attached SCSI disk Feb 23 14:54:48 node2 iscsid: Could not set session2 priority. READ/WRITE throughout and latency could be affected. Feb 23 14:54:48 node2 iscsid: Connection2:0 to [target: iqn local.itzgeek.server:disk1, portal: ,326 0] through [iface: default] is operational now List down the attached disks. [root@node1 ~]# cat /proc/partitions major minor #blocks name sda sda sda sr dm dm dm sdb Format the new disk (for the sake of article, I have formatted whole disk instead of creating partition) root@node1 ~]# mkfs.xfs /dev/sdb

8 meta-data=/dev/sdb isize=256 agcount=8, agsize= blks = sectsz=512 attr=2, projid32bit=1 = crc=0 data = bsize=4096 blocks= , imaxpct=25 = sunit=0 swidth=0 blks naming =version 2 bsize=4096 ascii-ci=0 ftype=0 log =internal log bsize=4096 blocks=2560, version=2 = sectsz=512 sunit=0 blks, lazy-count=1 realtime =none extsz=4096 blocks=0, rtextents=0 Mount the disk. [root@node1 ~]# mount /dev/sdb /mnt Verify the disk is mounted using the below command. [root@node1 ~]# df -ht Filesystem Type Size Used Avail Use% Mounted on /dev/mapper/centos-root xfs 50G 955M 50G 2% / devtmpfs devtmpfs 908M 0 908M 0% /dev tmpfs tmpfs 914M 54M 861M 6% /dev/shm tmpfs tmpfs 914M 8.5M 905M 1% /run tmpfs tmpfs 914M 0 914M 0% /sys/fs/cgroup /dev/mapper/centos-home xfs 48G 33M 48G 1% /home /dev/sda1 xfs 497M 97M 401M 20% /boot /dev/sdb xfs 5.0G 33M 5.0G 1% /mnt Automount iscsi storage To automount the iscsi storage during every reboot, you would need to make an entry in /etc/fstab file.

9 Before updating the /etc/fstab file, get the UUID of the iscsi disk using the following command. Replace /dev/sdb with your iscsi disk name. blkid /dev/sdb /dev/sdb: LABEL="/" UUID="9df472f4-1b0f-41c0-a6eb-89574d2caee3" TYPE="xfs" Now, edit the /etc/fstab file. vi /etc/fstab Make an entry something like below. # # /etc/fstab # Created by anaconda on Tue Jan 30 02:14: # # Accessible filesystems, by reference, are maintained under '/dev/disk' # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info # UUID=9df472f4-1b0f-41c0-a6eb-89574d2caee3 / xfs defaults 0 0 UUID=c7469f92-75ec-48ac-b42d-d5b89ab75b39 /mnt xfs _netdev 0 0 Remove iscsi storage In case you want to de-attach the added disk, please follow the procedure (unmount and logout). [root@node1 ~]# umount /mnt/ [root@node1 ~]# iscsiadm -m node -T iqn local.itzgeek.server:disk1 -p u Logging out of session [sid: 1, target: iqn local.itzgeek.server:disk1, portal: ,3260] Logout of [sid: 1, target: iqn local.itzgeek.server:disk1, portal: ,3260] successful. That s All.