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How does mdadm add devices to an array?
Add a single device to an appropriate array. If the addition of the device makes the array runnable, the array will be started. This provides a convenient interface to a hot-plug system. As each device is detected, mdadm has a chance to include it in some array as appropriate.
What do you need to know about mdadm in Linux?
mdadm is a tool for creating, managing, and monitoring RAID devices using the md driver in Linux. Some common tasks, such as assembling all arrays, can be simplified by describing the devices and arrays in this configuration file. SYNTAX The file should be seen as a collection of words separated by white space (space, tab, or newline).
What does the first mode of mdadm do?
This is the first of the two modes you will use a lot. As the name implies, it creates arrays, and writes the superblocks for arrays that have them. It also fires off initialisation – making sure that the disks of a mirror are identical, or that on a parity array the parities are correct.
How is mdadm used in a hot plug system?
This provides a convenient interface to a hot-plug system. As each device is detected, mdadm has a chance to include it in some array as appropriate. This is for doing things to specific components of an array such as adding new spares and removing faulty devices.
How big does mdadm version 1.0 need to be?
Version 1.0 will leave 128K at the end of each device if it is large enough – “large enough” being defined as 200GB. mdadm is unable to move the superblock, so there is no way of converting between the different version 1s. There are also two other superblock formats, ddf and imsm.
Why does mdadm say device or resource busy?
Trying to build a RAID 1 with a device that is mounted, mdadm says “Device or resource busy”, even with –force. If –force worked the backup would still be at risk of being inconsistent as some older writes to the device may not have finished and new writes may occur.
Which is the default config file for mdadm?
Specify the config file. Default is to use /etc/mdadm.conf, or if that is missing then /etc/mdadm/mdadm.conf. If the config file given is partitions then nothing will be read, but mdadm will act as though the config file contained exactly DEVICE partitions and will read /proc/partitions to find a list of devices to scan.
Why is the MISC mode assumed in mdadm?
If a device is given before any options, or if the first option is –add, –fail, or –remove, then the MANAGE mode is assumed. Anything other than these will cause the Misc mode to be assumed.
How does mdadm check for a bona fide array?
Components can be explicitly given or can be searched for. mdadm checks that the components do form a bona fide array, and can, on request, fiddle superblock information so as to assemble a faulty array. Build an array that doesn’t have per-device superblocks.