RAID磁盤陣列詳解

1、RAID磁盤陣列(RedundantArraysofInexpensiveDisks,RAID),有“價格便宜具有冗余能力的磁盤陣列”之意。原理是利用數(shù)組方式來作磁盤組,配合數(shù)據(jù)分散排列的設(shè)計,提升數(shù)據(jù)的安全性。磁盤陣列是由很多價格較便宜的磁盤,組合成一個容量巨大的磁盤組,利用個別磁盤提供數(shù)據(jù)所產(chǎn)生加成效果提升整個磁盤系統(tǒng)效能。利用這項技術(shù),將數(shù)據(jù)切割成許多區(qū)段,分別存放在各個硬盤上。磁盤陣列還能利用同位檢皿ParityCheck)的觀念，在數(shù)組中任一顆硬盤故障時，仍可讀出數(shù)據(jù)，在數(shù)據(jù)重構(gòu)時，將數(shù)據(jù)經(jīng)計算后重新置入新硬盤中。2塊以上的硬盤即可,成本低,可以提高整個磁盤的性能和吞吐量。RAID0

2、(條帶(strping)是組建磁盤陣列中最簡單的一種形式,只需要RAID0沒有提供冗余或錯誤修復(fù)能力,但實現(xiàn)成本是最低的。特點：速度快,沒有容錯能力BRAIDLEVELOzStrtpedDiskArraywilhoutFaultToleranceServer)ARAJDControllerwww恥n匚camCopyright1S9ti-2075AeFw怦口&Cwpontiort/yFightsRAID1：鏡像(mirroring)ID1稱為磁盤鏡像,原理是把一個磁盤的數(shù)據(jù)鏡像到另一個磁盤上,也就是說數(shù)據(jù)在寫入一塊磁盤的同時,會在另一塊閑置的磁盤上生成鏡像文件,在不影響性能情況下最大限度的保證系

3、統(tǒng)的可靠性和可修復(fù)性上,只要系統(tǒng)中任何一對鏡像盤中至少有一塊磁盤可以使用,甚至可以在一半數(shù)量的硬盤出現(xiàn)問題時系統(tǒng)都可以正常運行,當(dāng)一塊硬盤失效時,系統(tǒng)會忽略該硬盤,轉(zhuǎn)而使用剩余的鏡像盤讀寫數(shù)據(jù),具備很好的磁盤冗余能力。雖然這樣對數(shù)據(jù)來講絕對安全，但是成本也會明顯增加，磁盤利用率為50%，以四塊80GB容量的硬盤來講，可利用的磁盤空間僅為160GB。另外，出現(xiàn)硬盤故障的RAID系統(tǒng)不再可靠，應(yīng)當(dāng)及時的更換損壞的硬盤，否則剩余的鏡像盤也出現(xiàn)問題，那么整個系統(tǒng)就會崩潰。更換新盤后原有數(shù)據(jù)會需要RAID1多用在保很長時間同步鏡像，外界對數(shù)據(jù)的訪問不會受到影響，只是這時整個系統(tǒng)的性能有所下降。因此，存關(guān)

4、鍵性的重要數(shù)據(jù)的場合。RAID1示意圖RAID5：條帶+分布校驗3塊以上，利用率皿n1)/n,有容錯功能，最多可以壞一塊磁盤RAIDLEVEL5:IndependentDataDiskswithDistributedParityBlock?AncwnwzMHEAElocksBBlacksCBlocks.DBlatziuESecluQright翅19軸-290、AtfvncficfComakrter&ecwr%Cwp=22=3=4容錯功能無有有較強讀寫速度最快寫入慢1B較快較快磁盤空間利用100%50%n-1n-2mdadm命令：mdadm-manageMD(mutipledisk)device

5、sakaLinuxSoftwareRAIDCurrently,LinuxsupportsLINEARmddevices,RAID0(striping),RAID1(mirroring),RAID4,RAID5,RAID6,RAID10,MULTIPATH,FAULTY,andCONTAINER.-C:新建RAID設(shè)備-l：設(shè)定RAID級別n：磁盤數(shù)目：設(shè)定RAID成員設(shè)備數(shù)目-x(sparedevice)：磁盤數(shù)目，設(shè)定備用磁盤數(shù)目-s:掃描配置文件/etc/madam.conf-D：查看RAID設(shè)備信息-S：停用RAID-A：激活RAIDrootlvm#cat/proc/mdstat查看RA

6、ID的配置信息Personalities:raid6raid5raid4md5:activeraid5sde5sdf4(S)sdd2sdc1sdb03144192blockssuper1.2level5,512kchunk,algorithm24/4UUUUunuseddevices:rootlvm#mdadm-Ds查看設(shè)備信息ARRAY/dev/md5metadata=1.2spares=1name=lvm:5UUID=e433a3d5:94c67839:5e66cae5:e4976d17創(chuàng)建RAID5mdadm-C/dev/md5-l5-n4-x1/dev/sdbcdef查看RAID的詳細(xì)

7、信息mdadm-D/dev/md5創(chuàng)建配置文件mdadm-Ds/etc/mdadm.conf停止RAIDmdadm-S/dev/md5查看RAID信息cat/proc/mdstat格式化掛載RAIDODDOmkfs.ext4/dev/md5自動掛載RAIDDO修改/etc/fstab注:/boot分區(qū)用于存放引導(dǎo)文件，不用應(yīng)用RAID機制RAID5模擬故障讓失效的/dev/sdbl替換為/dev/sdglmdadm/dev/md5-a/dev/sdg1-r/dev/sdb1配置共享的熱備份磁盤多個RAID共享備份磁盤節(jié)約空間修改mdadm.conf文件添加spare-groupsparedis

8、ksmonitor開啟監(jiān)控RAID多種元數(shù)據(jù)格式-Es查看成員設(shè)備上的元數(shù)據(jù)信息-zero-superblock清空成員設(shè)備上的元數(shù)據(jù)信息rootlocalhost#mdadm-E/dev/sdb查看磁盤上的元數(shù)據(jù)千萬不要在沒有關(guān)閉RAID的情況下刪除分區(qū)正確關(guān)閉RAIDODDumount卸載RAID文件系統(tǒng)mdadm-SOORAID清空/etc/mdadm.conf文件清除/etc/fstab中RAID的掛載記錄清除每塊磁盤上的元數(shù)據(jù)刪除/dev/下所對應(yīng)的raid設(shè)備rootlvm#cat/proc/mdstat查看RAID的配置信息Personalities:raid6raid5raid

9、4md5:activeraid5sde5sdf4(S)sdd2sdc1sdb03144192blockssuper1.2level5,512kchunk,algorithm24/4UUUUunuseddevices:rootlvm#mdadm-DsARRAY/dev/md5metadata=1.2spares=1name=lvm:5UUID=e433a3d5:94c67839:5e66cae5:e4976d17練習(xí)：1.新建raid5卷，使用4塊磁盤作raid5,1塊磁盤作熱備rootlocalhostDesktop#mdadm-C/dev/md5-l5-n4-x1/dev/sdbcdefmd

10、adm:Defaultingtoversion1.2metadatamdadm:array/dev/md5started.rootlocalhostDesktop#cat/proc/mdstat查看RAID的配置信息Personalities:raid6raid5raid4md5:activeraid5sde5sdf4(S)sdd2sdc1sdb0可知sdf4做了熱備盤3144192blockssuper1.2level5,512kchunk,algorithm24/4UUUUrootlocalhostDesktop#mdadm-D/dev/md5查看/dev/md5的設(shè)備信息/dev/md5

11、:Version:1.2CreationTime:SunJul2101:19:252013RaidLevel:raid5ArraySize:3144192(3.00GiB3.22GB)UsedDevSize:1048064(1023.67MiB1073.22MB)RaidDevices:4TotalDevices:5Persistence:SuperblockispersistentUpdateTime:SunJul2101:19:332013State:cleanActiveDevices:4WorkingDevices:5FailedDevices:0SpareDevices:1Layou

12、t:left-symmetricChunkSize:512KName:lvm:5(localtohostlvm)UUID:e433a3d5:94c67839:5e66cae5:e4976d17Events:18rootlocalhostDesktop#mdadm-Ds/etc/mdadm.conf創(chuàng)建配置文件rootlocalhostDesktop#mdadm-S/dev/md5停止RAIDmdadm:stopped/dev/md5rootlocalhostDesktop#mdadm-A/dev/md5激活RAIDmdadm:/dev/md5hasbeenstartedwith4drivesa

13、nd1spare.rootlocalhostDesktop#mkfs.ext4/dev/md52.格式化raid5設(shè)備rootlocalhostDesktop#mkfs.ext4/dev/md5格式化md53.掛載使用rootlocalhostDesktop#mkdir/filerootlocalhostDesktop#mount/dev/md5/file4.自動掛載功能，修改/etc/fstab文件，添加在/etc/fstab寫入/devsda5/fileext4defaults00rootlocalhostDesktop#mdadm-D/dev/md5格式化及掛載后，再次查看md5設(shè)備信息

14、/dev/md5:5.讓其中的一塊失效，然后看raid5是否能夠繼續(xù)使用NumberMajorMinorRaidDeviceState08160activesync/dev/sdb18321activesync/dev/sdc28482activesync/dev/sdd58643activesync/dev/sde4880sparerootlocalhostDesktop#mdadm/dev/md5-f/dev/sdd（先失效一塊）rootlocalhostDesktop#mdadm/dev/md5-f/dev/sde（后失效一塊）使用cat/proc/mdstat命令查看修復(fù)過程（需趕快查

15、看，才能看到效果）容量一致刪除有問題的磁盤，添加一個好的磁盤作熱備，要求磁盤mdadm/dev/md5-r/dev/sdede-a/dev/sd【gh】rootlocalhost#cat/proc/mdstat查看raid的構(gòu)建過程Personalities:raid6raid5raid4md5:activeraid5sde5sdf4（S）sdd2sdc1sdb03144192blockssuper1.2level5,512kchunk,algorithm24/3UUU_=recovery=68.5%（719232/1048064）finish=0.0minspeed=143846K/secr

16、ootlocalhostfile#mdadm-D/dev/md5/dev/md5:Version:1.2CreationTime:SunJul2101:19:252013RaidLevel:raid5ArraySize:3144192(3.00GiB3.22GB)UsedDevSize:1048064(1023.67MiB1073.22MB)RaidDevices:4TotalDevices:5Persistence:SuperblockispersistentUpdateTime:SunJul2101:44:492013State:cleanActiveDevices:4WorkingDev

17、ices:5FailedDevices:0SpareDevices:1Layout:left-symmetricChunkSize:512KName:lvm:5(localtohostlvm)UUID:e433a3d5:94c67839:5e66cae5:e4976d17Events:68NumberMajorMinorRaidDeviceState08160activesync/dev/sdb18321activesync/dev/sdc48802activesync/dev/sdf681123activesync/dev/sdh5896spare/dev/sdg/dev/sdhrootlo

18、calhostfile#mdadm/dev/md5-f/dev/sdh再次破壞rootlocalhostfile#mdadm-D/dev/md5ActiveDevices:4WorkingDevices:4FailedDevices:1NumberMajorMinorRaidDeviceState08160activesync/dev/sdb18321activesync/dev/sdc48802activesync/dev/sdf96activesync/dev/sdg68112faultyspare/dev/sdhrootlocalhostfile#mdadm/dev/md5-f/dev/

19、sdhrootlocalhostfile#mdadm-D/dev/md5/dev/md5:State:clean,degraded,recoveringActiveDevices:3WorkingDevices:4FailedDevices:1SpareDevices:1NumberMajorMinorRaidDeviceState08160activesync/dev/sdb18321activesync/dev/sdc48802activesync/dev/sdf58963sparerebuilding/dev/sdg68112-faultyspare/dev/sdh【rootlocalhostfile#mdadm/dev/md5-f/dev/sdf破壞/sdf盤ActiveDevices:2WorkingDevices:2FailedDevices:3NumberMajorMinorRaidDeviceState08160activesync/dev/sdb18321activesync/dev/sdc2002removed3003removed4880-faultyspare/dev/sdf5