Introduction to the SCSI TARGET (1) Foundation of linux I Pot O Stack
We introduced the preview aspect of the linux Imax O stack earlier. I took a brief look at the composition of the entire linux Iamp O stack.
Starting from today, we will introduce in detail the derived linux Imax O stack, linux Imax O target, which is the export of the Imax O stack.
I. basic introduction
What is the Icano export protocol stack?
In a broad sense, people may come into contact with this thing every day.
For example, the mobile hard drive we use every day also has an Imax O export protocol stack inside it, but since it does not involve the parsing of the Imax O command, it only does the work of transferring from SATA to USB.
In fact, the hard disk itself is also a standard specification exported by Ihammer O, and the specification it uses is often implemented in the back-end storage protocol (SAS, SATA, etc.).
Well, what I mainly introduce today is the front-end export of the Icano protocol stack, which mainly includes: iscsi, fiber channel and other common ways.
In history, there are many exports of the IET O protocol stack, such as IET (iSCSI Enterprise Target), which I first contacted. He can only export iscsi target, and SCST. He is more comprehensive debug, which is recommended by many hba card manufacturers.
We focus on the LIO maintained by the linux mainline, that is, the target module in the kernel.
The architecture of linux linux O target is clear, and the management from the top is implemented by CLI.
CLI is supported by / usr/lib/python3/dist-packages/rtslib_fb and so on.
Rtslib_fb creates target kernel support by manipulating the directories and files under the / sys/kernel/config/target directory.
Target's configfs in the kernel is a complex set of code used to manage instances of target in kernel.
The target core module is implemented by the kernel, which mainly does the simulation work of SCSI CMD and can provide a variety of advanced capabilities.
For example, from the perspective of cluster, persistent reservations,ALUA (asymmetric logical unit assigntment) is supported.
REFERRALS features, fence features, etc. Ability to implement advanced VAAI features, which are mainly used in vmware exsi.
The main SCSI commands such as unmap,zero,write same,xcopy can also be applied to other virtualized storage platforms.
Storage management engine includes: standard storage, memory map and RDMA and other functions.
The lowest layer of fabric mod is mainly export protocol-driven support.
Storage mod, mainly to provide backend category support.
[this article is only posted by 51cto blogger "underlying Storage Technology" https://blog.51cto.com/12580077, official account release: storage Valley], if you need to reprint, please contact me, thank you.
