{"id":373,"date":"2018-06-24T18:32:47","date_gmt":"2018-06-24T16:32:47","guid":{"rendered":"http:\/\/hentati.org\/?p=373"},"modified":"2020-12-06T20:45:02","modified_gmt":"2020-12-06T19:45:02","slug":"373","status":"publish","type":"post","link":"https:\/\/hentati.org\/index.php\/2018\/06\/24\/373\/","title":{"rendered":"Linux RAID Software : Set Up RAID 1"},"content":{"rendered":"

In this tutorial, we\u2019ll be talking about\u00a0RAID<\/strong>, specifically we will set up\u00a0software RAID 1<\/strong>\u00a0on a running Linux distribution.<\/span><\/p>\n

What is RAID?<\/span><\/h2>\n

RAID stands for\u00a0R<\/strong>edundant\u00a0A<\/strong>rray of\u00a0I<\/strong>nexpensive\u00a0D<\/strong>isks. RAID allows you to turn multiple physical hard drives into a single logical hard drive. There are many RAID levels such as RAID 0, RAID 1, RAID 5, RAID 10 etc.<\/span><\/p>\n

Here we will discuss about\u00a0RAID 1<\/strong>\u00a0which is also known as\u00a0disk mirroring<\/strong>. RAID 1 creates identical copies of data. If you have two hard drives in RAID 1, then data will be written to both drives. The two hard drives have the same data.<\/span><\/p>\n

The nice part about RAID 1 is that if one of your hard drive fails, your computer or server would still be up and running because you have a complete, intact copy of the data on the other hard drive. You can pull the failed hard drive out while the computer is running, insert a new hard drive and it will automatically rebuilds the mirror.<\/span><\/p>\n

The downside of RAID 1 is that you don\u2019t get any extra disk space. If your two hard drives are both 1TB, then the total usable volume is 1TB instead of 2TB.<\/span><\/p>\n

Hardware RAID vs Software RAID<\/span><\/h2>\n

To set up RAID, you can either use a hard drive controller, or use a piece of software to create it. A hard drive controller is a PCIe card that you put into a computer. Then you connect your hard drives to this card. When you boot up the computer, you are going to see an option that allows you to configure the RAID. You can install an operating system on top of hardware RAID which can increase uptime.<\/span><\/p>\n

Software RAID requires you already installed an operating system. It\u2019s good for storing data.<\/span><\/p>\n

Basic Steps to Create Software RAID 1 on Linux<\/span><\/h2>\n
    \n
  • First you need to have a Linux distribution installed on your hard drive. In this tutorial we will name it\u00a0\/dev\/sda<\/code>.<\/span><\/li>\n
  • Then you are going to grab two hard drives which will be named\u00a0\/dev\/sdb<\/code>\u00a0and\u00a0\/dev\/sdc<\/code>\u00a0in this post. These two hard drives can be of different sizes. Remember to back up your existing data before formating your hard drives.<\/span><\/li>\n
  • Next, we will create special file systems on\u00a0\/dev\/sdb<\/code>\u00a0and\u00a0\/dev\/sdc<\/code>.<\/span><\/li>\n
  • And finally create the\u00a0RAID 1 array<\/strong>\u00a0using the\u00a0mdadm<\/code>\u00a0utility.<\/span><\/li>\n<\/ul>\n

    Step 1: Format Hard Drive<\/span><\/h2>\n

    Insert two hard drives into your Linux computer, then open up a terminal window. Run the following command to check the device name.<\/span><\/p>\n

    sudo fdisk -l<\/span><\/pre>\n
     <\/p>\n
    You can see mine is\u00a0\/dev\/sdb<\/code>\u00a0and\u00a0\/dev\/sdc<\/code>.<\/span><\/p>\n
    Then run the following 2 commands to make new MBR partition table on the two hard drives. (Note: this is going to wipe out all existing partitions and data from these two hard drives. Make sure your data is backed up.)<\/span><\/p>\n
    sudo parted \/dev\/sdb mklabel msdos\r\n\r\nsudo parted \/dev\/sdc mklabel msdos<\/span><\/pre>\n
    You can create\u00a0GPT partition table\u00a0by replacing\u00a0msdos<\/code>\u00a0with\u00a0gpt<\/code>, but for the sake of compatibility, this tutorial will create MBR partition table.<\/span><\/p>\n
    Next, use the\u00a0fdisk<\/code>\u00a0command to create a new partition on each drive and format them as a\u00a0Linux raid autodetect<\/strong>\u00a0file system. First do this on\u00a0\/dev\/sdb<\/code>.<\/span><\/p>\n
    sudo fdisk \/dev\/sdb<\/span><\/pre>\n
    Follow these instructions.<\/span><\/p>\n
      \n
    1. Type\u00a0n<\/strong>\u00a0to create a new partition.<\/span><\/li>\n
    2. Type\u00a0p<\/strong>\u00a0to select primary partition.<\/span><\/li>\n
    3. Type\u00a01<\/strong>\u00a0to create \/dev\/sdb1.<\/span><\/li>\n
    4. Press Enter<\/strong>\u00a0to choose the default first sector<\/span><\/li>\n
    5. Press Enter<\/strong>\u00a0to choose the default last sector. This partition will span across the entire drive.<\/span><\/li>\n
    6. Typing\u00a0p<\/strong>\u00a0will print information about the newly created partition. By default the partition type is Linux.<\/span><\/li>\n
    7. We need to change the partition type, so type\u00a0t<\/strong>.<\/span><\/li>\n
    8. Enter\u00a0fd<\/strong>\u00a0to set partition type to\u00a0Linux raid autodetect<\/code>.<\/span><\/li>\n
    9. Type\u00a0p<\/strong>\u00a0again to check the partition type.<\/span><\/li>\n
    10. Type\u00a0w<\/strong>\u00a0to apply the above changes.<\/span><\/li>\n<\/ol>\n
       <\/p>\n
      Follow the same instruction to create a Linux raid autodetect partition on\u00a0\/dev\/sdc<\/code>.<\/span><\/p>\n
      Now we have two raid devices\u00a0\/dev\/sdb1<\/code>\u00a0and\u00a0\/dev\/sdc1<\/code>.<\/span><\/p>\n
      Step 2: Install mdadm<\/span><\/h2>\n
      mdadm<\/code>\u00a0is used for managing MD (multiple devices) devices, also known as Linux software RAID.<\/span><\/p>\n
      Debian\/Ubuntu: \u00a0 \u00a0 sudo apt install mdadm\r\n\r\nCentOS\/Redhat: \u00a0 \u00a0 sudo yum install mdadm\r\n\r\nSUSE: \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0sudo zypper install mdadm\r\n\r\nArch Linux \u00a0 \u00a0 \u00a0 \u00a0 sudo pacman -S mdadm<\/span><\/pre>\n
      Let\u2019s examine the two devices.<\/span><\/p>\n
      sudo mdadm --examine \/dev\/sdb \/dev\/sdc<\/span><\/pre>\n
       <\/p>\n
      You can see that both are the type\u00a0fd<\/strong>\u00a0(Linux raid autodetect). At this stage, there\u2019s no RAID setup on\u00a0\/dev\/sdb1<\/code>\u00a0and\u00a0\/dev\/sdc1<\/code>\u00a0which can be inferred with this command.<\/span><\/p>\n
      sudo mdadm --examine \/dev\/sdb1 \/dev\/sdc1<\/span><\/pre>\n
       <\/p>\n
      Step 3: Create RAID 1 Logical Drive<\/span><\/h2>\n
      Execute the following command to create RAID 1. The logical drive will be named\u00a0\/dev\/md0<\/code>.<\/span><\/p>\n
      sudo mdadm --create \/dev\/md0 --level=mirror --raid-devices=2 \/dev\/sdb1 \/dev\/sdc1<\/span><\/pre>\n
      Now we can check it with:<\/span><\/p>\n
      cat \/proc\/mdstat<\/span><\/pre>\n
       <\/p>\n
      You can see that md0 is active and is a RAID 1 setup. To get more detailed information about\u00a0\/dev\/md0<\/code>, we can use the below commands:<\/span><\/p>\n
      sudo mdadm --detail \/dev\/md0<\/span><\/pre>\n
       <\/p>\n
      To obtain detailed information about each raid device, run this command:<\/span><\/p>\n
      sudo mdadm --examine \/dev\/sdb1 \/dev\/sdc1<\/span><\/pre>\n
      Step 4: Create File System on the RAID 1 Logical Drive<\/span><\/h2>\n
      Let\u2019s format it to ext4 file system.<\/span><\/p>\n
      sudo mkfs.ext4 \/dev\/md0<\/span><\/pre>\n
      Then create a mount point\u00a0\/mnt\/raid1<\/code>\u00a0and mount the RAID 1 drive.<\/span><\/p>\n
      sudo mkdir \/mnt\/raid1\r\n\r\nsudo mount \/dev\/md0 \/mnt\/raid1<\/span><\/pre>\n
      You can use this command to check how much disk space you have.<\/span><\/p>\n
      df -h \/mnt\/raid1<\/span><\/pre>\n
       <\/p>\n
      Step 5: Test<\/span><\/h2>\n
      Now let\u2019s go to\u00a0\/mnt\/raid1<\/code>\u00a0and create a text file.<\/span><\/p>\n
      cd \/mnt\/raid1\r\n\r\nsudo nano raid.txt<\/span><\/pre>\n
      Write something like<\/span><\/p>\n
      This is raid 1 device.<\/span><\/pre>\n
      Save and close the file. Next, remove one of your drive out from your computer and check the status RAID 1 device again.<\/span><\/p>\n
      sudo mdadm --examine \/dev\/sdb1 \/dev\/sdc1<\/span><\/pre>\n
       <\/p>\n
      You can see that\u00a0\/dev\/sdc1<\/code>\u00a0is not available. If we check\u00a0\/dev\/md0<\/code>, we can see that one RAID device is removed.<\/span><\/p>\n
      sudo mdadm --detail \/dev\/md0<\/span><\/pre>\n
       <\/p>\n
      However, the text file is still there.<\/span><\/p>\n
      cat \/mnt\/raid1\/raid1.txt<\/span><\/pre>\n
       <\/p>\n
      To add the failed drive (in this case\u00a0\/dev\/sdc1<\/code>) back to the RAID, run the following command.<\/span><\/p>\n
      sudo mdadm --manage \/dev\/md0 --add \/dev\/sdc1<\/span><\/pre>\n
       <\/p>\n
      It\u2019s very important to save our RAID1 configuration with the below command.<\/span><\/p>\n
      sudo mdadm --detail --scan --verbose | sudo tee \/etc\/mdadm\/mdadm.conf<\/span><\/pre>\n
      Output:<\/span><\/p>\n
      ARRAY \/dev\/md\/0 level=raid1 num-devices=2 metadata=1.2 spares=1 name=xenial:0 UUID=c7a2743d:f1e0d872:b2ad29cd:e2bee48c\r\n\u00a0 \u00a0 \u00a0 devices=\/dev\/sdb1,\/dev\/sdc1<\/span><\/pre>\n
      On some Linux distribution such as CentOS, the config file for\u00a0mdadm<\/code>\u00a0is\u00a0\/etc\/mdadm.conf<\/code>.<\/span><\/p>\n
      To automatically mount the RAID 1 logical drive on boot time, add an entry in\u00a0\/etc\/fstab<\/code>\u00a0file like below.<\/span><\/p>\n
      \/dev\/md0  \/mnt\/raid1  ext4  defaults  0  0<\/span><\/pre>\n","protected":false},"excerpt":{"rendered":"
      In this tutorial, we\u2019ll be talking about\u00a0RAID, specifically we will set up\u00a0software RAID 1\u00a0on a running Linux distribution. What is RAID? RAID stands for\u00a0Redundant\u00a0Array of\u00a0Inexpensive\u00a0Disks. RAID allows you to turn …<\/p>\n","protected":false},"author":1,"featured_media":378,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[8],"tags":[],"_links":{"self":[{"href":"https:\/\/hentati.org\/index.php\/wp-json\/wp\/v2\/posts\/373"}],"collection":[{"href":"https:\/\/hentati.org\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/hentati.org\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/hentati.org\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/hentati.org\/index.php\/wp-json\/wp\/v2\/comments?post=373"}],"version-history":[{"count":8,"href":"https:\/\/hentati.org\/index.php\/wp-json\/wp\/v2\/posts\/373\/revisions"}],"predecessor-version":[{"id":646,"href":"https:\/\/hentati.org\/index.php\/wp-json\/wp\/v2\/posts\/373\/revisions\/646"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/hentati.org\/index.php\/wp-json\/wp\/v2\/media\/378"}],"wp:attachment":[{"href":"https:\/\/hentati.org\/index.php\/wp-json\/wp\/v2\/media?parent=373"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/hentati.org\/index.php\/wp-json\/wp\/v2\/categories?post=373"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/hentati.org\/index.php\/wp-json\/wp\/v2\/tags?post=373"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}