计算机系统SCSI

今天装vm环境，我发现配置SCSI，需要选择LSI logic。

SCSI控制器的英文名称是“Small Computer System Interface”，中文翻译为"小型计算机系统专用接口"；顾名思义，这是为了小型计算机设计的扩充接口，它可以让计算机加装其他外设设备以提高系统性能或增加新的功能，例如硬盘、光驱、扫描仪等。

早期的计算机依速度、功能被区分为大型主机、小型计算机、微型计算机等多种等级,部分小型工作站、服务器属于小型计算机,而个人计算机属于微型计算机;因此当时使用SCSI接口的机种也以工作站、服务器等中高档设备为主。近年来则因个人计算机性能、扩充需求均大增,使SCSI在PC（普通微机）的应用也越来越多。

其实,SCSI也不算是新的接口类型,从有人注意到小型计算机功能延伸的问题、开始发展新的统一扩充接口、并在1986年正式订下SCSI的标准，至今也经历了将近20年的时间。早期Apple（苹果电脑）公司率先将SCSI选定为Macs计算机的标准接口,许多外设都借此统一接口与主系统连接。在PC方面则因为SCSI接口卡和设备昂贵,并且几乎各种外设都有较便宜的接口可替代,SCSI并未受到青睐；相对的,可用的SCSI设备也就不多了。反观今天,支持SCSI接口的外设产品从原本仅有硬盘、磁带机两种,增加到扫描仪、光驱、刻录机、MO等各种设备,大家接触SCSI的机会正在逐步增加中;再加上制造技术的进步,SCSI卡与外设的价格都已经不再高高在上,显示SCSI市场已经相当成熟。

Bus Logic 和 LSI Logic 都是虚拟硬盘 SCSI 设备的类型，它们的主要区别如下：

性能方面

• Bus Logic：是一种较老的技术，I/O 性能相对较差。
• LSI Logic：对性能进行了改进，对于小文件的读取速度有提高，整体性能优于 Bus Logic。

兼容性方面

• Bus Logic：对一些旧版本的操作系统兼容性较好，如 Windows 95 到 Windows 2000 默认支持 Bus Logic。
• LSI Logic：兼容性较好，适用于大多数现代操作系统，如 Windows Server 2003、Windows Vista、Windows Server 2008 等。

接口方面

• Bus Logic：具有并行接口。
• LSI Logic：具有并行接口，而 LSI Logic SAS 具有串行接口。

Windows 10 支持情况

Windows 10 支持 LSI Logic。Bus Logic 由于其较老的技术特性，通常不推荐在现代操作系统如 Windows 10 中使用。

• 真实 SCSI：是实际的硬件设备接口，需要物理的 SCSI 控制器卡、SCSI 线缆以及连接的 SCSI 存储设备等硬件组件来实现数据传输。例如，在传统的服务器系统中，通过安装 SCSI 控制器卡，连接 SCSI 磁盘阵列，来为服务器提供高速的存储访问功能。
• 虚拟 SCSI：是在虚拟化环境中模拟出来的 SCSI 接口。它并不依赖于真实的物理硬件设备，而是通过虚拟化软件在虚拟机内部创建一个虚拟的 SCSI 控制器，来连接虚拟的存储设备，如虚拟硬盘。比如在 VMware 虚拟化平台上，为虚拟机配置虚拟 SCSI 控制器，使虚拟机能够像操作真实 SCSI 设备一样来读写虚拟硬盘数据。

Introduction to VMware and its controllers

VMware is a leader in the virtualization space, and its powerful controller architecture plays a key role in its success. VMware's controllers are designed to improve performance and scalability while reducing complexity. The controllers are responsible for managing data flow between the host and virtual machines, and they can be configured to optimize performance in different ways.

The three main types of controllers supported by VMware are: SCSI, LSI Logic SAS, and Paravirtual. SCSI and LSI Logic SAS controllers are designed to optimize performance for traditional hard disk drives, while Paravirtual controllers are designed to optimize performance for solid-state drives. In addition, VMware also supports NVMe controllers, which are optimized for non-volatile memory express (NVMe) devices.

Understanding SCSI Controllers

SCSI controllers are the most widely used type of controller in VMware environments, and they are designed to improve performance and scalability. They are responsible for managing the flow of data between the host and virtual machines, and they can be configured to optimize performance in different ways.

SCSI controllers are divided into two types: LSI Logic SAS and Paravirtual. The LSI Logic SAS controller is best suited for traditional hard disk drives, while the Paravirtual controller is best suited for solid-state drives.

SECTION 2.1. LSI Logic SAS Controller

The LSI Logic SAS controller is a type of SCSI controller designed to optimize performance for traditional hard disk drives. This controller utilizes advanced features such as SCSI-3 persistent reservations, which allow multiple nodes to access data without conflicting with each other. This controller also supports command queuing, which allows multiple commands to be sent to a device at the same time, resulting in improved performance.

In addition, the LSI Logic SAS controller also supports advanced features such as hot-swapping, which allows you to add or remove hard disk drives without powering down the system. This ensures that your system stays available and running even when performing maintenance.

SECTION 2.2. Paravirtual Controller

The Paravirtual controller is a type of SCSI controller designed to optimize performance for solid-state drives. This controller utilizes advanced features such as command queuing, which allows multiple commands to be sent to a device at the same time. This allows for improved performance when dealing with large amounts of data.

In addition, the Paravirtual controller also supports advanced features such as thin provisioning, which allows you to allocate storage space on demand. This ensures that you can make the most out of your storage space and get the most out of your virtual environment.

Unlocking the Power of NVMe Controllers

NVMe controllers are the latest type of controller supported by VMware, and they are designed to optimize performance for non-volatile memory express (NVMe) devices. These controllers utilize advanced features such as command queuing, which allows multiple commands to be sent to a device at the same time. This allows for improved performance when dealing with large amounts of data.

In addition, NVMe controllers also support advanced features such as solid-state drive overcommitting, which allows you to allocate storage space on demand. This ensures that you can make the most out of your storage space and get the most out of your virtual environment.