iSCSI target(Server) setup/config on Linux(RHEL,CentOS,SL etc..)
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iSCSI is an Internet Protocol (IP)-based storage networking standard for linking data storage facilities. By carrying SCSI commands over IP networks, iSCSI is used to facilitate data transfers over intranets and to manage storage over long distances.
iSCSI is a client-server protocol. the server side is called ‘target’, while the client side is referred as the ‘ initiator’. Both target and initiator are uniquely identified by a string called the iSCSI Qualified Name(iQN).
Clients (called Initiators) sends SCSI commands (CDBs) to SCSI storage devices (Linux-IO Targets) on remote servers over internet. Unlike traditional Fibre Channel, which requires special-purpose cabling, iSCSI can be run over long distances using existing network infrastructure.
There are two different type of target, one is hardware based(iSCSI storage box), the other is software based. Here I’m going to show you how to config server side target on Linux. In this example, I’m using SL6.4, same to RHEL6.4, CentOS6.4, also can be reference to other Linux distributions.
Package installation
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# yum install scsi-target-utils.x86_64 iscsi-initiator-utils.x86_64 ================================================================================================ Package Arch Version Repository Size ================================================================================================ Installing: iscsi-initiator-utils x86_64 6.2.0.873-10.el6 sl 685 k scsi-target-utils x86_64 1.0.24-10.el6 sl 174 k Installing for dependencies: perl-Config-General noarch 2.52-1.el6 sl 71 k sg3_utils x86_64 1.28-5.el6 sl 470 k Transaction Summary =============================================================================================== Install 4 Package(s) Total download size: 1.4 M Installed size: 4.1 M Is this ok [y/N]: y Installed: iscsi-initiator-utils.x86_64 0:6.2.0.873-10.el6 scsi-target-utils.x86_64 0:1.0.24-10.el6 Dependency Installed: perl-Config-General.noarch 0:2.52-1.el6 sg3_utils.x86_64 0:1.28-5.el6 |
Start iSCSI target service
To start target service
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# service tgtd start Starting SCSI target daemon: [ OK ] |
To stop target service
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# service tgtd stop Stopping SCSI target daemon: [ OK ] |
Add device to iSCSI target
Two ways to add device to iSCSI target. The following examples in different way creates a target with id 1 (the iqn is iqn.2015-01.com.fibrevillage.pps11:pps11.target1) and adds a logical unit (backed by a block device /dev/mapper/ddnlun1) with lun 1.
Note:
backing-store or direct-store directives where backing-store refers to either a file or a block device, and direct-store refers to local SCSI devices. In the example below, it’s a block device.
Command line, using tgtadm and tgt-admin
Step1: Create a target device
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# tgtadm --lld iscsi --op new --mode target --tid 1 -T iqn.2015-01.com.fibrevillage.pps11:pps11.target1 |
Step2: Add a logic unit
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# tgtadm --lld iscsi --op new --mode logicalunit --tid 1 --lun 1 -b /dev/mapper/ddnlun1 |
Step3: Enable target to accept any initiator
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# tgtadm --lld iscsi --op bind --mode target --tid 1 -I ALL |
Step4: Save the configuration
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# tgt-admin --dump default-driver iscsi <target iqn.2015-01.com.fibrevillage.pps11:pps11.target1> backing-store /dev/mapper/ddnlun1 </target> # tgt-admin --dump >>targets.conf |
Direct modify the configuration file, /etc/tgt/targets.conf
Add the following lines to /etc/tgt/targets.conf
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default-driver iscsi <target iqn.2015-01.com.fibrevillage.pps11:pps11.target1> backing-store /dev/mapper/ddnlun1 </target> |
Then, restart tgt service, that’s it.
Note about iSCSI IQN:
- iSCSI Qualified Name (IQN)
- Format: The iSCSI Qualified Name is documented in RFC 3720, with further examples of names in RFC 3721. Briefly, the fields are:
-
- literal iqn (iSCSI Qualified Name)
- date (yyyy-mm) that the naming authority took ownership of the domain
- reversed domain name of the authority (e.g. org.alpinelinux, com.example, to.yp.cr)
- Optional “:” prefixing a storage target name specified by the naming authority.
- From the RFC:
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Naming String defined by Type Date Auth "example.com" naming authority +--++-----+ +---------+ +-----------------------------+ | || | | | | | iqn.1992-01.com.example:storage:diskarrays-sn-a8675309 iqn.1992-01.com.example iqn.1992-01.com.example:storage.tape1.sys1.xyz iqn.1992-01.com.example:storage.disk2.sys1.xyz<sup id="cite_ref-10" class="reference"><a href="http://en.wikipedia.org/wiki/ISCSI#cite_note-10">[10]</a></sup> |
List iSCSI targets
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# tgtadm --lld iscsi --op show --mode target Target 1: iqn.2015-01.com.fibrevillage.pps11:pps11.target1 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: 8001581 MB, Block size: 512 Online: Yes Removable media: No Prevent removal: No Readonly: No Backing store type: rdwr Backing store path: /dev/mapper/ddnlun1 Backing store flags: Account information: ACL information: ALL [root@pps11 tgt] |
Restart iSCSI target service
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# service tgtd restart Stopping SCSI target daemon: [ OK ] Starting SCSI target daemon: [ OK ] |
Query iSCSI target
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# tgt-admin -s Target 1: iqn.2015-01.com.fibrevillage.pps11:pps11.target1 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: 8001581 MB, Block size: 512 Online: Yes Removable media: No Prevent removal: No Readonly: No Backing store type: rdwr Backing store path: /dev/mapper/ddnlun1 Backing store flags: Account information: ACL information: ALL |
More advanced parameters setting
Specify lun id instead of using auto assignment, add the following line in the targets.conf file for the target
lun 2
Also, you can add parameters such as
vendor info, product info etc..
Here is a small example:
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default-driver iscsi <target iqn.2015-01.fibrevillage.pps11:pps11.target1> backing-store /dev/mapper/ddnlun1 lun 2 write-cache off scsi_sn 0D6212C60100000 vendor_id fibrevillage product_id iscsi-soft product_rev 1.0 </target> |
More parameters you can find in default /etc/tgt/targets.conf,
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#iSNSServerIP 192.168.111.222 #iSNSServerPort 3205 #iSNSAccessControl On #iSNS On # Some more parameters which can be specified locally or globally: #scsi_id ... #scsi_sn ... #vendor_id ... #product_id ... #product_rev ... #sense_format ... #removable ... #online ... #readonly [1 | 0] - 1 means readonly and 0 is read-write #path ... #mode_page 8:0:18:0x10:0:0xff.... #mode_page 8:0:18:0x10:0:0xff.... #device-type ... #bs-type ... # backing store type - default rdwr, can be aio, mmap, etc... #allow-in-use yes # if specified globally, can't be overwritten locally ... |
For example, on iscsi client, you can see the output of the iscsi target device
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#<a href="http://fibrevillage.com/storage/51-linux-lsscsi-list-scsi-devices-or-hosts-and-their-attributes" rel="alternate"> lsscsi</a> |
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[6:0:0:0] storage IET Controller 0001 - [6:0:0:2] disk Fibrevil iscsi-soft 1.0 /dev/sdbf |
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