Iscsi workflow target and initiator

As enterprise-level data grows exponentially, traditional centralized storage solutions cannot meet their storage requirements. Therefore, the storage area network (SAN) technology is widely used, however, there are shortcomings such as short distance, expensive price, and complicated construction. The iscsi-Based IP Storage technology is a new network storage technology that integrates the IP network technology into storage I/O, what are the advantages of other data access protocols in building heterogeneous storage networks ?, It has become a hot topic in network storage technology.

Using the iSCSI protocol to build a storage network is low, open, large, and compatible. The main drawback is that the storage and network use the same physical interface, second, we need to frequently encapsulate SCSI commands into IP packets and parse out SCSI commands from the IP packet. These will increase the network bandwidth and processor burden, and affect the system response speed, this restricts the development of iscsl technology.

The typical I/O Process for accessing the iSCSI target device is:

① When a user sends an access request to an iscsitarget device, the application accesses the file system through a system call:

② The file system interprets this I/O command, analyzes the device and address where the I/O command is located, and then sends the request to the SCSI upper-layer driver:

③ The SCSI upper-layer driver converts the corresponding I/O commands into SCSI commands and sends them to the iSCSI initiator;

④ ISCSI initiator encapsulates and packages SCSI commands and sends them to the iSCSI target module through the network;

⑤ After receiving the iSCSI command package, the iscsl target module sends the SCSI command in the iSCSI command package to the SCSI underlying driver;

6. The SCSI underlying driver completes the I/O Request and returns the data to the user based on the original path.

Taking iSCSI read operations as an example, the specific process is as follows:

① Send the iSCSI command;

② Cache scheduling;

③ Read data;

④ Encapsulate data using the iSCSI protocol;

⑤ Transmit data encapsulated by the iSCSI protocol.