Chapter 27. Set up an iSCSI Target and Initiator
Note
When using the hal daemon with a large number of iSCSI LUNs, over several thousand, the
--child-timeout option should be used in order to avoid boot failures. The --child-timeout option sets the number of seconds to wait for all disk probes to run. For example, to force the hal daemon to wait 10 minutes and 30 seconds, the option would read --child-timeout=630. The default time is 250 seconds. While this means the hal daemon will take longer to start, it will give enough time for all disk devices to be recognized and avoid boot failures.
The reason for this work around is because in 2003 when the hal daemon was created, it was unusual to have more than a dozen iSCSI disks. It is for this reason, the hal daemon has been removed in Red Hat Enterprise Linux 7 and replaced with udisks.
For more information, see the following Red Hat Knowledgebase solution: haldaemon fails to start on system with a large number of disks in RHEL 5 and RHEL 6
27.1. iSCSI Target Creation
An iSCSI target can be a dedicated physical device in a network, or it can be an iSCSI software-configured logical device on a networked storage server. The target is the end point in SCSI bus communication. Storage on the target, accessed by an initiator, is defined by LUNs.
Procedure 27.1. Create an iSCSI Target
- Install
scsi-target-utils.~]# yum install scsi-target-utils
- Open port 3260 in the firewall.
~]# iptables -I INPUT -p tcp -m tcp --dport 3260 -j ACCEPT ~]# service iptables save
- Start and enable the target service.
~]# service tgtd start ~]# chkconfig tgtd on
- Allocate storage for the LUNs. In this example a new partition is being created for block storage.
~]# fdisk /dev/vdb Welcome to fdisk (util-linux 2.23.2). 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 0x43eb8efd. Command (m for help): n Partition type: p primary (0 primary, 0 extended, 4 free) e extended Select (default p): *Enter* Using default response p Partition number (1-4, default 1): *Enter* First sector (2048-2097151, default 2048): *Enter* Using default value 2048 Last sector, +sectors or +size{K,M,G} (2048-2097151, default 2097151): +250M Partition 1 of type Linux and of size 250 MiB is set Command (m for help): w The partition table has been altered! Calling ioctl() to re-read partition table. Syncing disks. - Edit the
/etc/tgt/targets.conffile to create the target.~]# cat /etc/tgt/targets.conf ... default-driver iscsi <target iqn.2015-06.com.example.test:target1> backing-store /dev/vdb1 initiator-address 10.10.1.1 </target>
In the above example a simple target containing one backing store and one allowed initiator has been created. It must be named with an iqn name in the format ofiqn.YYYY-MM.reverse.domain.name:OptionalIdentifier. The backing store is the device the storage is located on. The initiator-address is the IP address of the initiator to access the storage. - Restart the target service.
~]# service tgtd restart Stopping SCSI target daemon: [ OK ] Starting SCSI target daemon: [ OK ]
- Check the configuration.
~]# tgt-admin --show Target 1: iqn.2015.06.com.example.test: server System information: Driver: iscsi State: ready I_T nexus information: LUN information: Lun: 0 Type: controller SCSI ID: IET 00010000 SCSI SN: beaf10 Size: 0 MB, Block size: 1 Online: Yes Removable media: No Prevent removal: No Readonly: No Backing store type: null Backing store path: None Backing store flags: LUN: 1 Type: disk SCSI ID: IET 00010001 SCSI SN: beaf11 Size: 2147 MB, Block size: 512 Online: Yes Removable media: No Prevent removal: No Readonly: No Backing store type: rdwr Backing store path: /dev/vdb1 Backing store flags: Account information: ACL information: 10.10.1.1
