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[[Software RAID]] is performed via the Linux kernel. No RAID controller is required on the computer. If the computer has a Linux compatible RAID controller then hardware RAID can be used. [[Hardware RAID]] is not discussed here.mdadm is a Linux utility used to manage and monitor software RAID devices. It is used in modern GNU/Linux distributions in place of older software RAID utilities such as raidtools2 or raidtools. == Software RAID on 3.x Linux===== the /boot filesystem ===In the past the /boot filesystem must be used either without md support, or else with RAID1. With modern kernels the it is possible to load the MD support as a kernel module through the initramfs mechanism. This approach allows the /boot filesystem to be inside any RAID system without the need of a complex manual configuration. * In the past you couldn't put /boot inside the RAID array, now you can.So you have a couple options in order to have a setup where each drive can be bootable. One is to have a /boot partition on each drive, or the other involves having /boot within a RAID array.=== Mdadm ===The mdadm utility can be used to create and manage storage arrays. === Example: 3-way RAID-1 array ===The /boot partition is stored at /dev/md0. This installs GRUB to each disk, so that if one disk fails, you can boot off one of the other disks. # grub grub> find /grub/stage1 (hd0,0) (hd1,0) (hd2,0) grub> device (hd0) /dev/sda grub> root (hd0,0) grub> setup (hd0) grub> device (hd0) /dev/sdb grub> root (hd0,0) grub> setup (hd0) grub> device (hd0) /dev/sdc grub> root (hd0,0) grub> setup (hd0) grub> quit== Legacy Linux Software RAID ==Software RAID is performed via the Linux kernel. No RAID controller is required on the computer. If the computer has a Linux compatible RAID controller then hardware RAID can be used. Hardware RAID is not discussed here.For the most part software RAID functions under linux now as it did ten years ago. However, since the information in this section was collected over ten years ago it will be considered outdated.== Software RAID 1 Example ===== Software RAID 1 Example ===#Install RAID manager: mdadm apt-get install mdadm== Software RAID 5 Example ===== Software RAID 5 Example ===== (Q). Did everything load ok with RAID when I booted? ===== (Q). Did everything load ok with RAID when I booted? ===== (Q). Hows RAID doing now? or Has a drive died while its running? ===== (Q). Hows RAID doing now? or Has a drive died while its running? ===== (Q). What does it mean when I see "kicking hda1" or "kicking" whatever in the dmesg and RAID / the system will not start? ===== (Q). What does it mean when I see "kicking hda1" or "kicking" whatever in the dmesg and RAID / the system will not start? ===== (*). Useful command summary: ===== (*). Useful command summary: ===== (man). lsraid usage examples ===== (man). lsraid usage examples ===== Command Reference by Example ===== Command Reference by Example ===