【Day8】RAID Disk Array

一、What is a disk array

概念

RAID磁盘阵列是Redundant Array of Independent Disks的缩写,中文简称为独立冗余磁盘阵列.

Disk array is actually more pieces独立的硬盘组合成A group of large capacity hard disk,利用个别Hard disks provide data generated by addition effect提升The whole system performance hard disk,And by redundant data storage increaseAdd tolerance.

If you don't set up the disk array,Two pieces of hard disk in your computer's independent existence,互不干涉.When you will be saved The hard disk storage1时,硬盘2Without any interference,Lead to a disk free,造成性能浪费.The computer hard disk simultaneously run disk array will.

RAIDThere are many levels,At present in the industry recognized rating asRAID 0～7.Is not level, the higher theRAID越好,不同等级的RAIDOnly is an array of different functions罢了.没有绝对的谁好谁坏,According to the actual usage and demand to choose to set up the disk array level.

常见的RAID组合方式为：

RAID0、RAID1、RAID5、 RAID6、RAID1+0、RAID0+1

RAID0

 raid0一时爽,Data crematoria

        RAID0 俗称“条带”,它将两个或多个硬盘组成一个逻辑硬盘,容量是所有硬盘之和,因为是多个硬盘组合成一个,Property may be concurrent writes,写入速度提高,但此方式硬盘数据没有冗余,没有容错,一旦一个物理硬盘损坏,则所有数据均丢失.RAID0 适合 于对数据量大,但安全性要求不高的场景,比如音像、视频文件Storage, etc.

Raid0Minimum need two pieces of hard disk,It is dispersed to each hard disk to store the data,所以raid0拥有所有raidKinds of the most powerful storage performance.而raid0的The total available space capacityIs your hard disk number multiplied by the minimum capacity Amount of hard disk capacity,Continuous read and write performance is multiples of single disc（Except the random performance,How much is the single disc,raid之 After how many）.

总结：

        至少两块硬盘组成,Read and write ent,Store the ent,安全性极差,一旦损坏,全部完蛋;无校验,Does not provide data protection.

RAID1

        RAID1 俗称“镜像”,它最少由两个硬盘组成,且两个硬盘上存储的数据均相同,以 实现数据冗余.RAID1 读操作速度有所提高,写操作理论上与单硬盘速度一样,但由于数据需要同时写入所有硬盘,实际上稍为下降.容错性是所有组合方式里最好的,As long as there is a piece of hard disk 正常,则能保持正常工作.But it to hard disk capacityUtilization is the most 低,只有 50%,因而Cost is the highest.RAID1 适合对数据安全性要求非常高的场景, 比如存储数据库数据文件之类. Security is low compared with blastraid0,raid1It is very safe.Raid1只支持两块硬盘组raid 阵列,而实际容量只有最小的那块硬盘的容量.这是因为raid1并没有对存储性能有 任何提高,只是提高了数据的安全性.两块硬盘组成的raid1阵列中,每块硬盘的数 据都是完全一样的,两个硬盘是互相的镜像关系.

总结：

        Consists of two pieces of hard disk,The hard disk data stored on the same,一块硬盘损坏,数据不会丢失;Hard disk capacity utilization minimum,只有50%,Hard disk capacity utilization minimum,所有RAIDThe highest data security,只有50%,;无校验.

RAID5

        最少Is composed of three hard disk,它将数据分散存储于阵列中的每个硬盘,And accompanied by a数据校验位,数据位与校验位通过算法能相互验证,当丢失其中的一位时,RAID 控制器 能通过算法,Using the other two dataThe missing data to calculate reduction.因而 RAID5 最多能允许一个硬盘损坏,有容错性.RAID5 相对于其它的组合方式,在容错与成本方面有一个平衡,因而受到大多数使用者的欢迎.一般的磁盘阵列,最常使用的就是 RAID5 这种方式

        Raid5采用了硬盘分割的技术,最少需要三块硬盘才可以 组建raid5阵列,它没有数据冗余,而是Store the data parity way to each hard disk, 而其中一块硬盘用于备用,支持在线更换.Raid5允许一块硬盘损坏或者离线,This array can still read,但是处于降级状态,需要重建.所以Raid5硬盘的总容量是Least of all the hard disk hard disk capacityN-1倍.比如你用4块12THard disk groupraid5阵列,Actually you will have to 到一个36T的raid5阵列.性能上raid5Higher than single plate case,Either read write,但是不如raid0.

        Now the hard disk capacity is more and more big,raid5After the hard disk damage rebuild arrays more and long time.因为raid5 Based on parity to store the information,So I need to rebuild by calculationraid5阵列.In a single disk4T,4块 硬盘为例,The time required to rebuild such an array is often have4Days to a week or so,And the success rate is also 不是100%.And because the reconstruction when all hard disk array full,If the reconstruction when you There are other hard drive died,That all your data is also skip stone.

 RAID 5奇偶校验信息——Exclusive or operation算

1.Xor logic symbol：^

2.Xor logic definition With the fake,Vision is true（0^0=0,1^1=0, 0^1=1 ,1^0=1）

3.In the computer logic operations with1表示真,0表示假.

4.Examples of two bytes bitwise exclusive or：

01111001

11100111 ：Exclusive or operation ^

-------------------

10011110

假设一个3A digital model of an exclusive or operation

例：3块硬盘HD1,HD2,HD3The data information of the whole through the calibration plateHD4Deposit check letter

图解RAID 5

        RAIDThe preservation of the principle is to useBit StripingAnd the current mainstreamBlock Striping的分割方式,将Data分散 Save to the hard drive,When the hard drive is damaged, throughXOR运算,Again will exist in the other hard diskParity Blocks及Data StripeIn the magneticData BlocksCalculation and reconstruction dataRebuild.

复原：

总结：

        At least consists of three disk,Scattered data is stored in each dish,And every hard disk has a calibration data,Allows only a hard disk damage,This can restore data by algorithm.Reading ability is relatively high,Writing ability is relatively low.重建数据时,Once you have hard disk damage,All data loss.

RAID6

         是在 RAID5 的基础上改良而成的,RAID6 再将数据校验位增加一位,所以允许损坏的硬盘数量也由 RAID5 的一个增加到二个.由于同一阵列中两个硬盘同时损坏的概 率非常少,所以,RAID6 用增加一块硬盘的代价,换来了比 RAID5 更高的数据安全性.

                             

         RAID6 The parity check code with two kinds of distributed storage of independent disks structure,它是对 RAID5 的扩展, 主要是用于要求数据绝对不能出错的场合,Using the two kinds of parity value,所以需要 N+2 个磁盘,同时对控制器的设计变得十分复杂,写入速度也不好,Used to calculate the parity value And the time it takes to validate data correctness is more,造成了不必须的负载,很少人用.       

 

总结：

        比 RAID5 的数据安全性更高.Allows the damage to the two pieces of hard disk,Every hard disk has two check digit,造成了不必须的负载,很少人用. 

RAID10 

        是First the mirror data operation,然后再对数据进行分组,RAID 1 在这里就是一个冗余的备份阵列,而 RAID 0 则负责数据的读写阵列.至少要四块盘,两块做 raid0,另两块 做 raid1,RAID 10 对存储容量的利用率和 RAID 1 一样低,只有 50%..Raid1+0 方 案造成了 50%的磁盘浪费,但是它提供了 200%的速度和单磁盘损坏的数据安全性, 并且当同时损坏的磁盘不在同一 Raid1 中,就能保证数据安全性、RAID 10 能提供比 RAID 5 更好的性能.这种新结构的可扩充性不好,使用此方案比较昂贵

        Raid10Can be in one of the disk completely offline cases still work,And after inserting new hard disk to replace the bad plate according toraid1The number of rules According to the reconstruction of,Security compared with the pureraid0有了大幅度提高.

总结：

        First the mirror data operation,然后再对数据进行分组,The storage space utilization is50%,它提供了 200%的速度和单磁盘损坏的数据安全性