about Software RAID

boot loader

lilo

• ファイルシステムにXFSを使う等で、OSインストール時にliloを選択した場合はデフォルトで全てのミラーdiskのMBRにliloがインストールされる模様
  • RAID5でどうなるかは不明

mdadm

Ubuntu

• ​Ubuntu 8.10 技術概要 | Ubuntu Japanese Team #起動時のデグレードRAID設定

• /etc/initramfs-tools/conf.d/mdadm

  # BOOT_DEGRADED:
  # Do you want to boot your system if a RAID providing your root filesystem
  # becomes degraded?
  #
  # Running a system with a degraded RAID could result in permanent data loss
  # if it suffers another hardware fault.
  #
  # However, you might answer "yes" if this system is a server, expected to
  # tolerate hardware faults and boot unattended.
  
  BOOT_DEGRADED=false
  

• /etc/mdadm/mdadm.conf

  # instruct the monitoring daemon where to send mail alerts
  MAILADDR root
  

• /etc/default/mdadm

  # AUTOCHECK:
  #   should mdadm run periodic redundancy checks over your arrays? See
  #   /etc/cron.d/mdadm.
  AUTOCHECK=true
  
  # START_DAEMON:
  #   should mdadm start the MD monitoring daemon during boot?
  START_DAEMON=true
  

  • /etc/cron.d/mdadm

    # By default, run at 01:06 on every Sunday, but do nothing unless the day of
    # the month is less than or equal to 7. Thus, only run on the first Sunday of
    # each month. crontab(5) sucks, unfortunately, in this regard; therefore this
    # hack (see #380425).
    6 1 * * 0 root [ -x /usr/share/mdadm/checkarray ] && [ $(date +\%d) -le 7 ] && /usr/share/mdadm/checkarray --cron --all --quiet
    

dpkg-reconfigure mdadm

• [ ... ] がデフォルト値

• sudo dpkg-reconfigure mdadm
  1. /etc/default/mdadm AUTOCHECK

      ┌───────────────────────────┤ Configuring mdadm ├
      │                                                                           │
      │ If your kernel supports it (>> 2.6.14), mdadm can periodically check the  │
      │ redundancy of your MD arrays (RAIDs). This may be a resource-intensive    │
      │ process, depending on your setup, but it could help prevent rare cases    │
      │ of data loss. Note that this is a read-only check unless errors are       │
      │ found; if errors are found, mdadm will try to correct them, which may     │
      │ result in write access to the media.                                      │
      │                                                                           │
      │ The default, if turned on, is to run the checks on the first Sunday of    │
      │ every month at 01:06 o'clock.                                             │
      │                                                                           │
      │ Should mdadm run monthly redundancy checks of the MD arrays?              │
      │                                                                           │
      │                   [<Yes>]                      <No>                       │
      │                                                                           │
      └──────────────────────────────────────
     

  2. /etc/default/mdadm START_DAEMON

       ┌──────────────────────────┤ Configuring mdadm ├
     ─│                                                                         │
       │ The MD (RAID) monitor daemon sends email notifications in response to   │
       │ important MD events (such as a disk failure). You probably want to      │
       │ enable it.                                                              │
       │                                                                         │
       │ Do you want to start the MD monitoring daemon?                          │
       │                                                                         │
       │                   [<Yes>]                      <No>                     │
       │                                                                         │
       └──────────────────────────────────────
     

  3. /etc/mdadm/mdadm.conf MAILADDR

        ┌─────────────────────────┤ Configuring mdadm ├─
     ─ │ Please enter the email address of the user who should get the email   │
        │ notification for important MD events.                                 │
        │                                                                       │
        │ Recipient for email notifications:                                    │
        │                                                                       │
        │ root_________________________________________________________________ │
        │                                                                       │
        │                                <Ok>                                   │
        │                                                                       │
        └─────────────────────────────────────
     

  4. /etc/initramfs-tools/conf.d/mdadm BOOT_DEGRADED

      ┌───────────────────────────┤ Configuring mdadm ├
      │                                                                           │
      │ If your root filesystem is on a RAID, and a disk is missing at boot, it   │
      │ can either boot with the degraded array, or hold the system at a          │
      │ recovery shell.                                                           │
      │                                                                           │
      │ Running a system with a degraded RAID could result in permanent data      │
      │ loss if it suffers another hardware fault.                                │
      │                                                                           │
      │ If you do not have access to the server console to use the recovery       │
      │ shell, you might answer "yes" to enable the system to boot unattended.    │
      │                                                                           │
      │ Do you want to boot your system if your RAID becomes degraded?            │
      │                                                                           │
      │                    <Yes>                      [<No>]                      │
      │                                                                           │
      └──────────────────────────────────────
     

  • apply settings...

     * Stopping MD monitoring service mdadm --monitor                        [ OK ]
    Generating array device nodes... done.
     Removing any system startup links for /etc/init.d/mdadm-raid ...
    update-initramfs: Generating /boot/initrd.img-2.6.24-24-server
    Warning: LBA32 addressing assumed
    Added Linux *
    Added LinuxOLD
    The Master boot record of  /dev/sda  has been updated.
    Warning: /dev/sdb is not on the first disk
    The Master boot record of  /dev/sdb  has been updated.
    2 warnings were issued.
     * Starting MD monitoring service mdadm --monitor                        [ OK ]