iSCSI Workflow Target and initiator

With the exponential growth of enterprise-class data, the traditional centralized storage scheme cannot meet its storage requirements, so the storage area network (storage region Network,san) technology is widely used, but its existence is short, the price is expensive and the construction is complex. IP storage technology based on iSCSI protocol is an emerging network storage technology, which integrates IP network technology into storage I/O, and has the incomparable advantage of other data access protocols in constructing heterogeneous storage network.

The use of iSCSI protocol to build a storage network, with low, open, large capacity, compatibility and so on, and its main disadvantage is that the storage and network use the same physical interface, followed by the need to frequently encapsulate SCSI commands in the IP packet and from the IP packet to resolve the SCSI command, All of them will increase the burden of network bandwidth and processor, and affect the response speed of the system, thus restricting the development of ISCSL technology.

The typical I/O process for accessing an iSCSI target device is:

① when a user makes an access request to a Iscsitarget device, the application accesses the file system through a system call:

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

③SCSI the upper-level driver converts the appropriate I/O command to a SCSI command and sends it to the iSCSI initiator;

④ISCSI Initiator encapsulates the SCSI command package and sends it over the network to the ISCSI target module;

⑤ISCSL the target module receives the iSCSI command Pack, the SCSI command in the iSCSI command Pack is sent to the SCSI underlying driver;

The ⑥ completes the I/O request by the SCSI underlying driver and returns the data to the user at the original path.

As an example of iSCSI read operations, the specific process is:

① send iSCSI commands;

② cache scheduling;

③ reading data;

④ data encapsulation using the iSCSI protocol;

The ⑤ transmits the data encapsulated by the iSCSI protocol.

iSCSI Workflow Target and initiator