文档介绍：第六章设备管理 Devices Management
RAID技术
缓冲技术
设备分配
磁盘阵列RAID技术
把多块硬盘当做一块逻辑硬盘来管理和存取数据以提高磁盘系统的稳定性和速度,并可提供容错功能
1988年提出
RAID可分成多级( Level )
数据在各盘中的分布
数据的冗余和校验处理
RAID
控制器
逻辑硬盘
Disk1
Disk2
.....
What is RAID?
Redundant Array of Inexpensive(Independent) Disks 廉价(独立)磁盘冗余阵列。
RAID的初衷主要是为大型服务器提供高端的存储功能和冗余的数据安全。
SCSI 与 IDE-RAID
RAID也有全软、半软半硬与全硬之分
Which are the various RAID levels and what is their exact meaning?
尽管各级RAID有不同的实现技术,但有两点相同:
都使用多个物理磁盘分布存储数据.
按独立于应用程序的方式存储数据(即数据的存储方式对应用程序是透明的)
RAID 0
Striped Disk Array without Fault Tolerance没有容错设计的条带磁盘阵列
多个硬盘并联在一起。RAID 0在存储数据时由RAID控制器(硬件或软件)分割成大小相同的数据条,同时写入阵列中的磁盘。
flash demo with RAID0
RAID 1 = Mirroring
Mirroring and Duplexing(相互镜像)
镜像——两个硬盘的内容完全一样,内容彼此备份。写入时,RAID控制器将数据同时写入两个硬盘。其中任何一个硬盘的数据出现问题,可以马上从另一个硬盘中进行恢复。
RAID Level 1 requires a minimum of 2 drives to implement
flash demo with RAID1
RAID0+1 = Stripping + Mirror
RAID Level 0+1 requires a minimum of 4 drives to implement
Very expensive / High overhead
flash demo with RAID 0+1
RAID10 = Mirroring + stripping
This can be found only in hardware RAID
RAID-bines RAID 0 and RAID 1 by striping data across multiple drives without parity and it mirrors the entire array to a second set of drives. This process delivers good performance and excellent data protection, but cuts the usable disk space in half. RAID-10 requires a minimum of four same-size drives, and is also the most expensive RAID solution and offers limited scalability.
flash demo with RAID 10 ( 1+0)