SCSI is a fast bus that can be able to connect to numerous devices at the same time. Among some of the hardware that SCSI is able to connect to include tape drivers, CD- ROM/RW drives, hard drives, scanners printers and other support devices. SCSI originally stood for Small Computer System Interface, but it's really outgrown the 'small' designation. It's a fast bus that can connect lots of devices to a computer at the same time, including hard drives, scanners, CD-ROM/RW drives, printers and tape drives. For internal SCSI peripherals, the SCSI ID usually is set by configuring a jumper on the peripheral. For external SCSI peripherals, the SCSI ID usually is set with a switch on the back of the peripheral. SCSI ID numbers don’t have to be sequential, as long as the SCSI host adapter card and each peripheral has a different number.
-->Starting with Windows 10, Version 2004 (OS build 19041.488 or higher), two additional identifiers are available for NVMe storage disk drives which support the STOR_RICH_DEVICE_DESCRIPTION structure:
SCSIt*v(8)p(40)
Where:
t* is a device type code of variable length
v(8) is an 8-character vendor identifier
p(40) is a 40-character product identifier
SCSIt*v(8)p(40)r(8)
Where:
t* is a device type code of variable length
v(8) is an 8-character vendor identifier
p(40) is a 40-character product identifier
r(8) is an 8-character revision level value
In versions of Windows prior to Windows 10, Version 2004 (OS build 19041.488 or higher), the device ID format for a small computer system interface (SCSI) device is as follows:
SCSIt*v(8)p(16)r(4)
Where:
t* is a device type code of variable length
v(8) is an 8-character vendor identifier
p(16) is a 16-character product identifier
r(4) is a 4-character revision level value
The bus enumerator determines the device type by indexing an internal string table, using a numerically encoded SCSI device type code, obtained by querying the device, as shown in the following table. The remaining components are just strings returned by the device, but with special characters (including space, comma, and any nonprinting graphic) replaced with an underscore.
The SCSI Port driver currently returns the following device type strings, the first nine of which correspond to standard SCSI type codes.
| SCSI type code | Device type | Generic type | Peripheral ID |
|---|---|---|---|
| DIRECT_ACCESS_DEVICE (0) | Disk | GenDisk | DiskPeripheral |
| SEQUENTIAL_ACCESS_DEVICE (1) | Sequential | TapePeripheral | |
| PRINTER_DEVICE (2) | Printer | GenPrinter | PrinterPeripheral |
| PROCESSOR_DEVICE (3) | Processor | OtherPeripheral | |
| WRITE_ONCE_READ_MULTIPLE_DEVICE (4) | Worm | GenWorm | WormPeripheral |
| READ_ONLY_DIRECT_ACCESS_DEVICE (5) | CdRom | GenCdRom | CdRomPeripheral |
| SCANNER_DEVICE (6) | Scanner | GenScanner | ScannerPeripheral |
| OPTICAL_DEVICE (7) | Optical | GenOptical | OpticalDiskPeripheral |
| MEDIUM_CHANGER (8) | Changer | ScsiChanger | MediumChangerPeripheral |
| COMMUNICATION_DEVICE (9) | Net | ScsiNet | CommunicationsPeripheral |
| 10 | ASCIT8 | ScsiASCIT8 | ASCPrePressGraphicsPeripheral |
| 11 | ASCIT8 | ScsiASCIT8 | ASCPrePressGraphicsPeripheral |
| 12 | Array | ScsiArray | ArrayPeripheral |
| 13 | Enclosure | ScsiEnclosure | EnclosurePeripheral |
| 14 | RBC | ScsiRBC | RBCPeripheral |
| 15 | CardReader | ScsiCardReader | CardReaderPeripheral |
| 16 | Bridge | ScsiBridge | BridgePeripheral |
| 17 | Other | ScsiOther | OtherPeripheral |
An example of a device ID for a disk drive would be as follows:
SCSIDiskSEAGATE_ST39102LW_______0004
There are four hardware IDs in addition to the device ID:
SCSIt*v(8)p(16)
SCSIt*v(8)
SCSIv(8)p(16)r(1)
V(8)p(16)r(1)
In the third and fourth of these additional identifiers, r(1) represents just the first character of the revision identifier. These hardware IDs are illustrated by the following examples:
SCSIDiskSEAGATE_ST39102LW_______
SCSIDiskSEAGATE_
SCSIDiskSEAGATE_ST39102LW_______0
SEAGATE_ST39102LW_______0
The SCSI Port driver supplies only one compatible ID, one of the variable-sized generic type codes from the previous table.
For example, the compatible ID for a disk drive is as follows:
GenDisk
The generic identifier is used in INF files for SCSI devices more than any other, because SCSI drivers are typically generic.
Be aware that the SCSI Port driver returns no generic name for sequential access and 'processor' devices.
Every IT industry needs storage for saving the increasing data day by day. There are different methods by which we can provide storage to our client servers like through SAN, NAS, DAS, iSCSI, etc. In this tutorial, we are going to learn how to share storage from the main server to the client machine using iSCSI target in Red Hat Enterprise Linux 7 (RHEL 7).
Sharing the storage through iSCSI (Internet Small Computer System Interface) is very economical and any machine can become target i.e. server which will provide the storage. This is a software based technique to provide storage to the client servers and requires “targetcli” rpm. And if you are preparing for RHCE exam, this is one of the objectives of the exam.
Basically, in this tutorial, we will learn how to configure or setup an iSCSI target using targetcli in RHEL7 or CentOS 7.
Step by Step Procedure to setup an iSCSI target in RHEL 7
1. First of all, verify if you have targetcli RPM or not. If not install it using OS native commands. We had the package already so it updated it using repo.
2. Now once the targetcli package is installed, enable and start it. Enable will make sure target service is active after every reboot.
3. Now add permanently iSCSI port 3260 to the firewall rule using the below commands and reload firewalld service.
Note: You won’t be able to see the port 3260 until you reload the firewalld service.
4. Now create a partition of the disk and set the size which you are going to share. You can also share a complete disk. Here, for example, we are creating 200MB partition with id “8e” for LVM and will create a logical volume (lv) with it.
Now you have to set configure your target and share the disk to the client. This is where actual work begins and should be done very carefully. We will use ‘targetcli’ command and then follow the steps given below.
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5. Enter command ‘targetcli’ to get an iSCSI CLI prompt.
6. Now, use the logical volume (/dev/iscsi_vg/iscsi_lv) created in step 4 to create a block storage object ‘iscsi_disk’.
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7. Then, create an IQN (iSCSI Qualified Name) called iqn.2018-06.com.server:client1.disk1. This will also create a default TPG (Target Portal Group).
If default portal is created, like above one, delete it. We will create a new one later.
8.Now, we will create an ACL in the TPG.
This ACL configures the target to only accept initiator connections from a client presenting iqn.2018-06.com.server:client2 as it’s initiator IQN, also name as initiator name.
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9. Create a lun for each backstores, here we have only 1 backstores, so we will create only 1 lun. This steps also activates the corresponding backstores.
10. Now create a portal to designate the listening IP address and ports. The IP given below is the IP of the client where you want to provide the storage.
The whole configuration should look like below. After that, you can exit the targetcli prompt.
11. Now, just restart the target service.
This was all about configuring your iSCSI target or iSCSI server and sharing to the client or iSCSI initiator. Hope you were able to understand and follow the steps. In case of any questions or doubt, please comment below. In the next article, we will see how to setup iSCSI initiator and mount the filesystem. So do not forget to subscribe our blog.
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