mdadm

Create array

$ sudo mdadm --create [/dev/md/MyRAID] --level [raid_level] --raid-devices [number_of_disks] [/dev/sdXN]

$ sudo mdadm --stop [/dev/md0]

$ sudo mdadm --fail [/dev/md0] [/dev/sdXN]

$ sudo mdadm --remove [/dev/md0] [/dev/sdXN]

$ sudo mdadm --assemble [/dev/md0] [/dev/sdXN]

$ sudo mdadm --detail [/dev/md0]

$ sudo mdadm --zero-superblock [/dev/sdXN]

mdadm [options] mdadm [options] --assemble mdadm [options] --create mdadm [options] --manage

--assemble
    Assemble a previously created array. Can also be used to start a stopped array.

--create
    Create a new RAID array.

--manage
    Modify or manage an existing array.

--detail
    Show detailed information about a RAID device.

--stop
    Deactivate a RAID array.

--add
    Add a spare disk to an array.

--remove
    Remove a disk from an array.

--fail
    Mark a device as failed.

--zero-superblock
    Remove RAID metadata from a device.

--level=level
    Specify the RAID level to use when creating an array (e.g., raid0, raid1, raid5, raid6, raid10).

--raid-devices=number
    Specify the number of active devices in the array.

--bitmap=internal
    Use the internal bitmap RAID feature.

--force
    Force an operation that would otherwise be refused.

The mdadm command is a utility used in Linux to manage software RAID (Redundant Array of Independent Disks) arrays. It allows you to create, manage, monitor, and troubleshoot RAID devices. Software RAID uses the Linux kernel's capabilities to provide data redundancy and performance improvements by combining multiple physical disks into a single logical volume. With mdadm, you can configure various RAID levels (RAID0, RAID1, RAID5, RAID6, RAID10, etc.), assemble existing arrays, monitor their health, add or remove drives, and perform recovery operations in case of disk failures. The command provides functionalities for creating a new RAID array, defining the desired RAID level, specifying the member disks, and starting the array. mdadm also allows you to query the status of RAID arrays, examine their configuration, and detect any issues, such as failed drives or inconsistencies. The utility can send notifications about events related to RAID arrays, such as drive failures or rebuild completion. mdadm is a powerful tool for managing software RAID in Linux and crucial for maintaining data integrity and availability on systems that rely on RAID technology.

Improper use can lead to data loss. Requires careful planning and understanding of RAID concepts. Permissions and device paths are critical.
It relies on the Linux kernel's RAID implementation; kernel support is essential.

mdadm uses a configuration file (typically /etc/mdadm/mdadm.conf) to store information about RAID arrays,
allowing arrays to be automatically assembled at boot time. Ensure this file is correctly configured for persistent RAID setup.

Regular monitoring of RAID arrays is crucial. mdadm can be configured to send email alerts upon drive failures or other critical events. Scripts can be integrated for more advanced monitoring.

In case of a drive failure, mdadm provides tools to rebuild the array onto a replacement drive. Ensure you have a suitable replacement drive available and understand the rebuild process before a failure occurs.

mdadm (Multiple Device Administration) was developed to provide a standardized way to manage software RAID arrays across different Linux distributions.
Its development began in the early 2000s, aiming to offer a more robust and feature-rich alternative to earlier RAID management tools.
Over time, it has become the standard tool for managing software RAID in Linux, with ongoing development to improve its capabilities and support new RAID levels and features.

mount(8), fsck(8), lvm(8)