1:Raid定義

RAID,全稱 Redundant Array of Inexpensive Disks,中文名為廉價磁盤冗余陣列.RAID可分為軟RAID和硬RAID,軟RAID是通過軟件實現(xiàn)多塊硬盤冗余的.而硬RAID是一般通過 RAID卡來實現(xiàn)RAID的.前者配置簡單,管理也比較靈活.對于中小企業(yè)來說不失為一最佳選擇.硬RAID往往花費比較貴.不過,在性能方面具有一定優(yōu) 勢.

2:RAID分類

RAID可分為以下幾種,做 個表格認識下:

RAID 0

存取速度最快 沒有容錯

RAID 1

完全容錯 成本高,硬盤使用率低.

RAID 3

寫入性能最好 沒有多任務功能

RAID 4

具備多任務及容錯功能 Parity 磁盤驅(qū)動器造成性能瓶頸

RAID 5

具備多任務及容錯功能 寫入時有overhead

RAID 0+1

速度快、完全容錯 成本高

3:Linux RAID 5實驗詳解

假設我有4塊硬盤,(沒有條件的朋友可以用虛擬機設置出4塊硬盤出來).分別為/dev/sda /dev/sdb /dev/sdc /dev/sdd.首先做的就是分區(qū)了.

[root@localhost /]# fdisk /dev/sda

Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel

Building a new DOS disklabel. Changes will remain in memory only,

until you decide to write them. After that, of course, the previous

content won't be recoverable.

Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)

Command (m for help): n #按n創(chuàng)建新分區(qū)

Command action

e extended

p primary partition (1-4) #輸入p 選擇創(chuàng)建主分區(qū)

p

Partition number (1-4): 1 #輸入 1 創(chuàng)建第一個主分區(qū)

First cylinder (1-130, default 1): #直接回車,選擇分區(qū)開始柱面這里就從 1 開始

Using default value 1

Last cylinder or +size or +sizeM or +sizeK (1-102, default 130):

Using default value 130

Command (m for help): w #然后輸入w寫盤

The partition table has been altered!

Calling ioctl() to re-read partition table.

Syncing disks.

其它分區(qū)照這樣做全部分出一個區(qū)出來.下面是總分區(qū)信息:

[root@localhost /]# fdisk -l

Disk /dev/sda: 1073 MB, 1073741824 bytes

255 heads, 63 sectors/track, 130 cylinders

Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot????? Start???????? End????? Blocks?? Id System

/dev/sda1?????????????? 1???????? 130???? 1044193+ 83 Linux

Disk /dev/sdb: 1073 MB, 1073741824 bytes

255 heads, 63 sectors/track, 130 cylinders

Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot????? Start???????? End????? Blocks?? Id System

/dev/sdb1?????????????? 1???????? 130???? 1044193+ 83 Linux

Disk /dev/sdc: 1073 MB, 1073741824 bytes

255 heads, 63 sectors/track, 130 cylinders

Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot????? Start???????? End????? Blocks?? Id System

/dev/sdc1?????????????? 1???????? 130???? 1044193+ 83 Linux

Disk /dev/sdd: 1073 MB, 1073741824 bytes

255 heads, 63 sectors/track, 130 cylinders

Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot????? Start???????? End????? Blocks?? Id System

/dev/sdd1?????????????? 1???????? 130???? 1044193+ 83 Linux

下一步就是創(chuàng)建RAID了.

[root@localhost ~]# mdadm --create /dev/md0 --level=5 --raid-devices=3 --spare-devices=1 /dev/sd[a-d]1????????????? #意思是創(chuàng)建RAID設備名為md0, 級別為RAID 5

mdadm: array /dev/md0 started.?? 使用3個設備建立RAID,空余一個做備用.

OK,初步建立了RAID了,我們看下具體情況吧.

[root@localhost ~]# mdadm --detail /dev/md0

/dev/md0:

Version : 00.90.01

Creation Time : Fri Aug 3 13:53:34 2007

Raid Level : raid5

Array Size : 2088192 (2039.25 MiB 2138.31 MB)

Device Size : 1044096 (1019.63 MiB 1069.15 MB)

Raid Devices : 3

Total Devices : 4

Preferred Minor : 0

Persistence : Superblock is persistent

Update Time : Fri Aug 3 13:54:02 2007

State : clean

Active Devices : 3

Working Devices : 4

Failed Devices : 0

Spare Devices : 1

Layout : left-symmetric

Chunk Size : 64K

Number?? Major?? Minor?? RaidDevice State

0?????? 8??????? 1??????? 0????? active sync?? /dev/sda1

1?????? 8?????? 17??????? 1????? active sync?? /dev/sdb1

2?????? 8?????? 33??????? 2????? active sync?? /dev/sdc1

3?????? 8?????? 49?????? -1????? spare?? /dev/sdd1?????????? UUID : e62a8ca6:2033f8a1:f333e527:78b0278a

Events : 0.2

讓RAID開機啟動.配置RIAD配置文件吧.默認名字為mdadm.conf,這個文件默認是不存在的,要自己建立.該配置文件存在的主要作 用是系統(tǒng)啟動的時候能夠自動加載軟RAID，同時也方便日后管理.

說明下,mdadm.conf文件主要由以下部分組成:DEVICES選項制定組成RAID所有設備, ARRAY選項指定陣列的設備名、RAID級別、陣列中活動設備的數(shù)目以及設備的UUID號.

[root@localhost ~]# mdadm --detail --scan > /etc/mdadm.conf

[root@localhost ~]# cat /etc/mdadm.conf

ARRAY /dev/md0 level=raid5 num-devices=3 UUID=e62a8ca6:2033f8a1:f333e527:78b0278a

devices=/dev/sda1,/dev/sdb1,/dev/sdc1,/dev/sdd1

#默認 格式是不正確的,需要做以下方式的修改:

[root@localhost ~]# vi /etc/mdadm.conf

[root@localhost ~]# cat /etc/mdadm.conf

devices /dev/sda1,/dev/sdb1,/dev/sdc1,/dev/sdd1

ARRAY /dev/md0 level=raid5 num-devices=3 UUID=e62a8ca6:2033f8a1:f333e527:78b0278a

將/dev/md0創(chuàng)建文件系統(tǒng),

[root@localhost ~]# mkfs.ext3 /dev/md0

mke2fs 1.35 (28-Feb-2004)

Filesystem label=

OS type: Linux

Block size=4096 (log=2)

Fragment size=4096 (log=2)

261120 inodes, 522048 blocks

26102 blocks (5.00%) reserved for the super user

First data block=0

Maximum filesystem blocks=536870912

16 block groups

32768 blocks per group, 32768 fragments per group

16320 inodes per group

Superblock backups stored on blocks:

32768, 98304, 163840, 229376, 294912

Writing inode tables: done

Creating journal (8192 blocks): done

Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 21 mounts or

180 days, whichever comes first. Use tune2fs -c or -i to override.內(nèi) 容

掛載/dev/md0到系統(tǒng)中去,我們實驗是否可用:

[root@localhost ~]# cd /

[root@localhost /]# mkdir mdadm

[root@localhost /]# mount /dev/md0 /mdadm/

[root@localhost /]# cd /mdadm/

[root@localhost mdadm]# ls

lost+found

[root@localhost mdadm]# cp /etc/services .

[root@localhost mdadm]# ls

lost+found services

好了,如果其中某個硬盤壞了會怎么樣呢?系統(tǒng)會自動停止這塊硬盤的工作,然后讓后備的那塊硬盤頂上去工 作.我們可以實驗下.

[root@localhost mdadm]# mdadm /dev/md0 --fail /dev/sdc1

mdadm: set /dev/sdc1 faulty in /dev/md0

[root@localhost mdadm]# cat /proc/mdstat

Personalities : [raid5]

md0 : active raid5 sdc1[3](F) sdd1[2] sdb1[1] sda1[0] # F標簽以為此盤為fail.

2088192 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]

unused devices:

如果我要移除一塊壞的硬盤或添加一塊硬盤呢?

#刪除一塊硬盤

[root@localhost mdadm]# mdadm /dev/md0 --remove /dev/sdc1

mdadm: hot removed /dev/sdc1

[root@localhost mdadm]# cat /proc/mdstat

Personalities : [raid5]

md0 : active raid5 sdd1[2] sdb1[1] sda1[0]

2088192 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]

unused devices:

#增加一塊硬盤

[root@localhost mdadm]# mdadm /dev/md0 --add /dev/sdc1

mdadm: hot added /dev/sdc1

[root@localhost mdadm]# cat /proc/mdstat

Personalities : [raid5]

md0 : active raid5 sdc1[3] sdd1[2] sdb1[1] sda1[0]

2088192 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]

unused devices:

好了,結(jié)束了.

總結(jié)

以上是生活随笔為你收集整理的linux支持raid5阵列,linux下raid5阵列的全部內(nèi)容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網(wǎng)站內(nèi)容還不錯，歡迎將生活随笔推薦給好友。