Linux hardware foundation

There is a real problem before learning what Linux is? doing what?

Baidu Encyclopedia explained:

Linux is a free to use and free dissemination of Unix-like operating system, is a POSIX and UNIX-based multi-user, multi-tasking, multi-threading and multi-CPU support for the operating system.

It can run major UNIX software tools, applications, and network protocols. It supports 32-bit and 64-bit hardware. Linux has inherited the design philosophy of Unix network-centric,

It is a stable performance in multi-user network operating system.

Linux operating system was born on October 5, 1991 (this is the first time officially made public). Linux, there are many different versions of Linux, but they all use the Linux kernel.

Linux can be installed in a variety of computer hardware devices, such as mobile phones, tablet PCs, routers, video game consoles, desktop computers, mainframes and supercomputers.

Strictly speaking, the word Linux itself, said Linux kernel, but in fact it has been used to describe the entire use Linux based on Linux kernel,

And use the operating system GNU project tools and databases.

　　　　　　　　　　　　　　　　　　　　　　　　　　-- https://baike.baidu.com/item/linux?wtp=tt

 

It can be seen Linux, currently the most important used in large enterprises, and large machinery,

 

This is the business use of server room, have said the ape - chicken factory.

So around the main scenario in terms of Linux

 

1. Server Category

1. Rack servers (primarily this).

2. Blade servers.

3. Tower server.

Server's foot:

1U Server: U is a unit, 1U = 4.45cm.

Server Core's power:

Dual power path AB.

Server Core calculation of CPU-

The number of CPU --- a few road.

There are four general 1cpu core.

Server Core's memory

Role: convergence of CPU and hard disk, CPU too fast, too slow hard drive, memory required convergence.

Features: After the power failure, the data disappear.

 

The core of the server disk

Interface: disk and server connection.

Interface Type: Interface type, the greater the interface, faster.

SATA: home, for less demanding server speed may also be used. Cheap, poor performance.

sas :服务器标配。性能、稳定性都好。

转速：rpm，每分钟转多少圈。5.4K、7.2K、10K、15K。

 

服务器核心之阵列卡（raid 卡）

1个非常大的文件 10000G 1000G。

1. 买个一 10000G (10T)硬盘。

2. 买 20 个 1000G 的硬盘。

做了raid之后的好处

统一管理硬盘；获得更高的容量;变得更加安全;速度更高。

 

 

程序、进程、守护进程

• 程序 -- 电影 --- 存放在硬盘上面。

• 进程 -- 看电影 --- 运行行起来的程序。

• 守护进程/服务 -- 持续看片住院 --- 一直运行的进程。

 

高并发写入

缺点：如何让你数据不丢（写在内存里，不能断电）

1. 两个电源 AB 路

2. UPS-不间断供电系统（蓄电池），能抗30 分钟到1个小时

3. 柴油发电机+油罐

4. 与附近的加油站签订一些紧急供油协议

 

buffer和cache

• buffer -- 观看视频的时候，有时候会看到转圈，那就是在把数据写入到你的内存中。存放这些数据的空间叫buffer，中文名叫缓冲区

• cache -- 提高观看速度，把其他地方的数据（尤其是硬盘里的）读取到内存中，然后在从内存中读取。

写buffet，读cache。写缓冲，读缓存。