1:Raid定義 RAID,全稱 Redundant Array of Inexpensive Disks,中文名為廉價(jià)磁盤冗余陣列.RAID可分為軟RAID和硬RAID,軟RAID是通過(guò)軟件實(shí)現(xiàn)多塊硬盤冗余的.而硬RAID是一般通過(guò) RAID卡來(lái)實(shí)現(xiàn)RAID的.前者配置簡(jiǎn)單,管理也比較靈活.對(duì)于中小企業(yè)來(lái)說(shuō)不失為一最佳選

1:Raid定義 ??RAID,全稱 Redundant Array of Inexpensive Disks,中文名為廉價(jià)磁盤冗余陣列.RAID可分為軟RAID和硬RAID,軟RAID是通過(guò)軟件實(shí)現(xiàn)多塊硬盤冗余的.而硬RAID是一般通過(guò) RAID卡來(lái)實(shí)現(xiàn)RAID的.前者配置簡(jiǎn)單,管理也比較靈活.對(duì)于中小企業(yè)來(lái)說(shuō)不失為一最佳選擇.硬RAID往往花費(fèi)比較貴.不過(guò),在性能方面具有一定優(yōu) 勢(shì). 2:RAID分類 RAID可分為以下幾種,做 個(gè)表格認(rèn)識(shí)下: RAID 0 存取速度最快 沒(méi)有容錯(cuò) RAID 1 完全容錯(cuò) 成本高,硬盤使用率低. RAID 3 寫入性能最好 沒(méi)有多任務(wù)功能 RAID 4 具備多任務(wù)及容錯(cuò)功能 Parity 磁盤驅(qū)動(dòng)器造成性能瓶頸 RAID 5 具備多任務(wù)及容錯(cuò)功能 寫入時(shí)有overhead RAID 0+1 速度快、完全容錯(cuò) 成本高 3:Linux RAID 5實(shí)驗(yàn)詳解 假設(shè)我有4塊硬盤,(沒(méi)有條件的朋友可以用虛擬機(jī)設(shè)置出4塊硬盤出來(lái)).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(gè)主分區(qū) First cylinder (1-130, default 1): #直接回車,選擇分區(qū)開(kāi)始柱面這里就從 1 開(kāi)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(gè)區(qū)出來(lái).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(shè)備名為md0, 級(jí)別為RAID 5 mdadm: array /dev/md0 started. ?? 使用3個(gè)設(shè)備建立RAID,空余一個(gè)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(kāi)機(jī)啟動(dòng).配置RIAD配置文件吧.默認(rèn)名字為mdadm.conf,這個(gè)文件默認(rèn)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(dòng)的時(shí)候能夠自動(dòng)加載軟RAID，同時(shí)也方便日后管理. 說(shuō)明下,mdadm.conf文件主要由以下部分組成:DEVICES選項(xiàng)制定組成RAID所有設(shè)備, ARRAY選項(xiàng)指定陣列的設(shè)備名、RAID級(jí)別、陣列中活動(dòng)設(shè)備的數(shù)目以及設(shè)備的UUID號(hào). [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(rèn) 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(shí)驗(yàn)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(gè)硬盤壞了會(huì)怎么樣呢?系統(tǒng)會(huì)自動(dòng)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(shí)驗(yàn)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(biāo)簽以為此盤為fail. ????? 2088192 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU] unused devices: <none> 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: <none> #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: <none> 好了,結(jié)束了.

轉(zhuǎn)載于:https://blog.51cto.com/flowstar/347485

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