RAID磁盘阵列详解

1、RAID磁盘阵列(RedundantArraysofInexpensiveDisks,RAID),有“价格便宜具有冗余能力的磁盘阵列”之意。原理是利用数组方式来作磁盘组,配合数据分散排列的设计,提升数据的安全性。磁盘阵列是由很多价格较便宜的磁盘,组合成一个容量巨大的磁盘组,利用个别磁盘提供数据所产生加成效果提升整个磁盘系统效能。利用这项技术,将数据切割成许多区段,分别存放在各个硬盘上。磁盘阵列还能利用同位检皿ParityCheck)的观念，在数组中任一颗硬盘故障时，仍可读出数据，在数据重构时，将数据经计算后重新置入新硬盘中。2块以上的硬盘即可,成本低,可以提高整个磁盘的性能和吞吐量。RAID0

2、(条带(strping)是组建磁盘阵列中最简单的一种形式,只需要RAID0没有提供冗余或错误修复能力,但实现成本是最低的。特点：速度快,没有容错能力BRAIDLEVELOzStrtpedDiskArraywilhoutFaultToleranceServer)ARAJDControllerwww恥n匚camCopyright1S9ti-2075AeFw怦口&Cwpontiort/yFightsRAID1：镜像(mirroring)ID1称为磁盘镜像,原理是把一个磁盘的数据镜像到另一个磁盘上,也就是说数据在写入一块磁盘的同时,会在另一块闲置的磁盘上生成镜像文件,在不影响性能情况下最大限度的保证系

3、统的可靠性和可修复性上,只要系统中任何一对镜像盘中至少有一块磁盘可以使用,甚至可以在一半数量的硬盘出现问题时系统都可以正常运行,当一块硬盘失效时,系统会忽略该硬盘,转而使用剩余的镜像盘读写数据,具备很好的磁盘冗余能力。虽然这样对数据来讲绝对安全，但是成本也会明显增加，磁盘利用率为50%，以四块80GB容量的硬盘来讲，可利用的磁盘空间仅为160GB。另外，出现硬盘故障的RAID系统不再可靠，应当及时的更换损坏的硬盘，否则剩余的镜像盘也出现问题，那么整个系统就会崩溃。更换新盘后原有数据会需要RAID1多用在保很长时间同步镜像，外界对数据的访问不会受到影响，只是这时整个系统的性能有所下降。因此，存关

4、键性的重要数据的场合。RAID1示意图RAID5：条带+分布校验3块以上，利用率皿n1)/n,有容错功能，最多可以坏一块磁盘RAIDLEVEL5:IndependentDataDiskswithDistributedParityBlock?AncwnwzMHEAElocksBBlacksCBlocks.DBlatziuESecluQright翅19轴-290、AtfvncficfComakrter&ecwr%Cwp=22=3=4容错功能无有有较强读写速度最快写入慢1B较快较快磁盘空间利用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设备-l：设定RAID级别n：磁盘数目：设定RAID成员设备数目-x(sparedevice)：磁盘数目，设定备用磁盘数目-s:扫描配置文件/etc/madam.conf-D：查看RAID设备信息-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查看设备信息ARRAY/dev/md5metadata=1.2spares=1name=lvm:5UUID=e433a3d5:94c67839:5e66cae5:e4976d17创建RAID5mdadm-C/dev/md5-l5-n4-x1/dev/sdbcdef查看RAID的详细

7、信息mdadm-D/dev/md5创建配置文件mdadm-Ds/etc/mdadm.conf停止RAIDmdadm-S/dev/md5查看RAID信息cat/proc/mdstat格式化挂载RAIDODDOmkfs.ext4/dev/md5自动挂载RAIDDO修改/etc/fstab注:/boot分区用于存放引导文件，不用应用RAID机制RAID5模拟故障让失效的/dev/sdbl替换为/dev/sdglmdadm/dev/md5-a/dev/sdg1-r/dev/sdb1配置共享的热备份磁盘多个RAID共享备份磁盘节约空间修改mdadm.conf文件添加spare-groupsparedis

8、ksmonitor开启监控RAID多种元数据格式-Es查看成员设备上的元数据信息-zero-superblock清空成员设备上的元数据信息rootlocalhost#mdadm-E/dev/sdb查看磁盘上的元数据千万不要在没有关闭RAID的情况下删除分区正确关闭RAIDODDumount卸载RAID文件系统mdadm-SOORAID清空/etc/mdadm.conf文件清除/etc/fstab中RAID的挂载记录清除每块磁盘上的元数据删除/dev/下所对应的raid设备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练习：1.新建raid5卷，使用4块磁盘作raid5,1块磁盘作热备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做了热备盘3144192blockssuper1.2level5,512kchunk,algorithm24/4UUUUrootlocalhostDesktop#mdadm-D/dev/md5查看/dev/md5的设备信息/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创建配置文件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设备rootlocalhostDesktop#mkfs.ext4/dev/md5格式化md53.挂载使用rootlocalhostDesktop#mkdir/filerootlocalhostDesktop#mount/dev/md5/file4.自动挂载功能，修改/etc/fstab文件，添加在/etc/fstab写入/devsda5/fileext4defaults00rootlocalhostDesktop#mdadm-D/dev/md5格式化及挂载后，再次查看md5设备信息

14、/dev/md5:5.让其中的一块失效，然后看raid5是否能够继续使用NumberMajorMinorRaidDeviceState08160activesync/dev/sdb18321activesync/dev/sdc28482activesync/dev/sdd58643activesync/dev/sde4880sparerootlocalhostDesktop#mdadm/dev/md5-f/dev/sdd（先失效一块）rootlocalhostDesktop#mdadm/dev/md5-f/dev/sde（后失效一块）使用cat/proc/mdstat命令查看修复过程（需赶快查

15、看，才能看到效果）容量一致删除有问题的磁盘，添加一个好的磁盘作热备，要求磁盘mdadm/dev/md5-r/dev/sdede-a/dev/sd【gh】rootlocalhost#cat/proc/mdstat查看raid的构建过程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再次破坏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破坏/sdf盘ActiveDevices:2WorkingDevices:2FailedDevices:3NumberMajorMinorRaidDeviceState08160activesync/dev/sdb18321activesync/dev/sdc2002removed3003removed4880-faultyspare/dev/sdf5