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: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/sdaDevice contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabelBuilding a new DOS disklabel. Changes will remain in memory only,until you decide to write them. After that, of course, the previouscontent 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创建新分区Command actione extendedp primary partition (1-4) #输入p 选择创建主分区pPartition 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,选择分区开始柱面这里就从 1 开始Using default value 1Last cylinder or +size or +sizeM or +sizeK (1-102, default 130):Using default value 130Command (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 -lDisk /dev/sda: 1073 MB, 1073741824 bytes255 heads, 63 sectors/track, 130 cylindersUnits = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System/dev/sda1 1 130 1044193+ 83 LinuxDisk /dev/sdb: 1073 MB, 1073741824 bytes255 heads, 63 sectors/track, 130 cylindersUnits = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System/dev/sdb1 1 130 1044193+ 83 LinuxDisk /dev/sdc: 1073 MB, 1073741824 bytes255 heads, 63 sectors/track, 130 cylindersUnits = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System/dev/sdc1 1 130 1044193+ 83 LinuxDisk /dev/sdd: 1073 MB, 1073741824 bytes255 heads, 63 sectors/track, 130 cylindersUnits = 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 5mdadm: array /dev/md0 started. 使用3个设备建立RAID,空余一个做备用.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 : 4Preferred Minor : 0 Persistence : Superblock is persistent Update Time : Fri Aug 3 13:54:02 2007 State : cleanActive Devices : 3Working Devices : 4Failed 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载软RAID，同时也方便日后管理.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.confARRAY /dev/md0 level=raid5 num-devices=3 UUID=e62a8ca6:2033f8a1:f333e527:78b0278a devices=/dev/sda1,/dev/sdb1,/dev/sdc1,/dev/sdd1#默认格式是不正确的,需要做以下方式的修改:[root@localhost ~]# vi /etc/mdadm.conf[root@localhost ~]# cat /etc/mdadm.confdevices /dev/sda1,/dev/sdb1,/dev/sdc1,/dev/sdd1ARRAY /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/md0mke2fs 1.35 (28-Feb-2004)Filesystem label=OS type: LinuxBlock size=4096 (log=2)Fragment size=4096 (log=2)261120 inodes, 522048 blocks26102 blocks (5.00%) reserved for the super userFirst data block=0Maximum filesystem blocks=53687091216 block groups32768 blocks per group, 32768 fragments per group16320 inodes per groupSuperblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912Writing inode tables: doneCreating journal (8192 blocks): doneWriting superblocks and filesystem accounting information: doneThis filesystem will be automatically checked every 21 mounts or180 days, whichever comes first. Use tune2fs -c or -i to override.内容挂载/dev/md0到系统中去,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]# lslost+found[root@localhost mdadm]# cp /etc/services .[root@localhost mdadm]# lslost+found services好了,如果其中某个硬盘坏了会怎么样呢?系统会自动停止这块硬盘的工作,然后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/sdc1mdadm: set /dev/sdc1 faulty in /dev/md0[root@localhost mdadm]# cat /proc/mdstatPersonalities : [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: none 如果我要移除一块坏的硬盘或添加一块硬盘呢?不然你大概会一直好奇和不甘吧——
详解Linux环境软RAID 5建立过程推荐
