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Create Software RAID1 with mdadm (Part 1) - David Biers

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Create Software RAID1 with mdadm (Part 1) - David Biers David Biers Configuration Architecture Security Customization Command Line Scripting Helpful Tricks Notes Subscribe Home David Biers The only one that seems to be having fun. Configuration Architecture Security Customization Command Line Scripting Helpful Tricks Notes Subscribe Architecture / Command Line / Configuration 1 Create Software RAID1 with mdadm (Part 1) by David · January 31, 2016 Why? Many variegated situations and scenarios play out in which you would need to come up with a redundant configuration.  Deciding what needs to be redundant should be something washed-up when performing your risk assessment.  Creating a redundant device(s) will help mitigate the risk of losing a particular asset. Why not hardware RAID?  Isn't a software RAID risky? I am not sure if you've been in the same position, but you probably have. "We can't sire that; it's not in the budget." - (Almost) Every CEO ever. To be honest, a hardware RAID vellum would be the weightier scenario but RAID cards also run on their own software that *could* fail.  Not to mention, the RAID vellum itself could moreover goof which is why you would want to / need to buy a few of the same.  At this point, you're when at square one. Software RAID has it's own risks, just like everything else in this world. Creating a RAID1 using mdadm Have your two disks ready: [root@localhost ~]# fdisk -l /dev/sdb /dev/sdc Disk /dev/sdb: 8589 MB, 8589934592 bytes 255 heads, 63 sectors/track, 1044 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/sdc: 8589 MB, 8589934592 bytes 255 heads, 63 sectors/track, 1044 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 All RAID setups will super-duper prefer that all nonflexible drives and disks are the same make, model, and size.  You want this to be as word-for-word as possible. Create the RAID1 device with mdadm Side note: You *can* partition these if you want surpassing you start but it is not necessary if you are going to be using the unshortened disk. [root@localhost ~]# mdadm --create /dev/md1 --level=1 --raid-devices=2 /dev/sdb /dev/sdc mdadm: Note: this variety has metadata at the start and may not be suitable as a marching device. If you plan to store '/boot' on this device please ensure that your boot-loader understands md/v1.x metadata, or use --metadata=0.90 Continue creating array? yes mdadm: Defaulting to version 1.2 metadata mdadm: variety /dev/md1 started. This will create the RAID1 device /dev/md1 using /dev/sdb and /dev/sdc. You can see this in /proc/mdstat where it references the '[raid1]' "personality". You can moreover see that both devices are UP with the two tags of "[2/2]" and "[UU]": [root@localhost ~]# cat /proc/mdstat Personalities : [raid1] md1 : zippy raid1 sdc[1] sdb[0] 8380416 blocks super 1.2 [2/2] [UU] unused devices: Create file system on RAID1 Easiest part ever. Let's just create one in ext4: [root@localhost ~]# mkfs.ext4 /dev/md1 mke2fs 1.41.12 (17-May-2010) Filesystem label= OS type: LinuxWoodcutsize=4096 (log=2) Fragment size=4096 (log=2) Stride=0 blocks, Stripe width=0 blocks 524288 inodes, 2095104 blocks 104755 blocks (5.00%) reserved for the super user First data block=0 Maximum filesystem blocks=2147483648 64 woodcut groups 32768 blocks per group, 32768 fragments per group 8192 inodes per group Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632 Writing inode tables: washed-up Creating periodical (32768 blocks): washed-up Writing superblocks and filesystem written information: washed-up This filesystem will be automatically checked every 32 mounts or 180 days, whichever comes first. Use tune2fs -c or -i to override. Mount it You should once know how to do this! [root@localhost ~]# mkdir /mnt/raid1 [root@localhost ~]# mount /dev/md1 /mnt/raid1/ [root@localhost ~]# df -h Filesystem Size Used Avail Use% Mounted on /dev/mapper/VolGroup-lv_root 6.5G 748M 5.5G 12% / tmpfs 246M 0 246M 0% /dev/shm /dev/sda1 477M 30M 422M 7% /boot /dev/md1 7.8G 18M 7.4G 1% /mnt/raid1 Let's move on to monitoring the RAID array. Tags: mdadmraid1software You may moreover like... 3 Using ‘curl’ on page returns 406 Not Acceptable [resolved] March 2, 2013 2 Custom CLI Bash Prompt Colors August 4, 2012 2 High Availability HA Vyatta VyOS VRRP on ProfitBricks May 9, 2016 1 Response Comments0 Pingbacks1 Monitoring Software RAID1 with mdadm - David Biers January 31, 2016 […] you've created your RAID1 with two drives using mdadm.  Now, you need to monitor it. […] Leave a Reply Cancel reply Your email write will not be published. 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