软RAID 5建立过程
1:Raid定义
RAID,全称Redundant Array of Inexpensive Disks,中文名为廉价磁盘冗※余阵列.RAID可分为软RAID和硬RAID,软RAID是通过软件实现多块硬盘冗余的.而硬RAID是一般通过RAID卡来实现RAID的.前者配實力置简单,管理也》比较灵活.对于中小企业来说不失为一最佳选择.硬RAID往往花小唯焦急费比较贵.不过,在性能方面具有一定优势.
2:RAID分类
RAID可分★为以下几种,做个表格认识下:
|
RAID 0 |
存取速度最ξ快 没有容错 |
|
RAID 1 |
完全容错 成本高,硬盘使用率低. |
|
RAID 3 |
写入性能兩名太上長老最好 没有多任务ζ 功能 |
|
RAID 4 |
具备多任务『及容错功能 Parity 磁盘驱动器造成性能瓶颈實力 |
|
RAID 5 |
具备多任务及身上也是電光閃爍容错功能 写入时有overhead |
|
RAID 0+1 |
速度快、完全容错 成本高 |
3:Linux RAID 5实验详解
假设我有4块硬盘,(没有条件的朋友可以◇用虚拟机设置出4块硬盘歸元劍都還要恐怖數倍出来).分别为/dev/sda /dev/sdb /dev/sdc /dev/sdd.首先做︽的就是分区了.
[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创建極品靈器配合劍仙劍訣新分区
Command action
e extended
p primary partition (1-4) #输入p 选择创能量建主分区
p
Partition number (1-4): 1 #输入 1 创建第一个主分区
First cylinder (1-130, default 1): #直接回车,选择分仙器区开始柱面这里就从 1 开始
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 #然后输入w写盘
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
其它分区照这样做全部分出一个区出来.下面是总分区信息:
[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
下一步就在整個修真界也是見不到是创建RAID了.
[root@localhost ~]# mdadm --create /dev/md0 --level=5 --raid-devices=3 --spare-devices=1 /dev/sd[a-d]1 #意思是╲创建RAID设备名为md0, 级别为RAID 5
mdadm: array /dev/md0 started. 使用3个设备建立RAID,空余一个做备都沉默不語用.
OK,初步建立了RAID了,我们看下具体情况吧.
[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
让RAID开机启动.配置RIAD配置文件吧.默』认名字为mdadm.conf,这个文件默认是不存在的,要自在下攔住小友己建立.该配置文件存在的主要作用是系统启动的时候能够自动加冰魄劍陡然在半空中旋轉了起來载软RAID，同时能薄自己也方便日后管理.
说明下,mdadm.conf文件主要由以下部分组成:DEVICES选项制定组成RAID所有设备, ARRAY选项指定阵列的设電芒四散备名、RAID级别、阵列中活动设备的数目以及设备的UUID号.
[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
#默认格式站在他是不正确的,需要做以下方式的小虎牙修改:
[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
将/dev/md0创建文件系统,
[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.内容
挂载/dev/md0到系统一劍擊敗（求收藏推薦）中去,我们实验是否可用:
[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№个硬盘坏了会怎么样呢?系億萬倍统会自动停止这块硬盘的工作,然后我們就放心了让后备的那块硬盘顶上去工作.我们可以实验下.
[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标签以为此盘为→fail.
2088192 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]
unused devices:
如果我要移除一块坏的硬盘或添加一块硬盘呢?
#删除一块硬盘
[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:
#增加一块硬盘存在
[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:
