[Bug 251646] Re: {upstream} missing command to start *single* arrays in "auto-read" mode (like --incremental)

[ceg]

Are you aware that starting all arrays degraded (what the initramfs
scripts currently have to do) is a serious bug? The replicas will
diverge, and if the non-rootfs devices become accessible later they need
to resync.

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https://bugs.launchpad.net/bugs/251646

Title:
  {upstream} missing command to start *single* arrays in "auto-read"
  mode (like --incremental)

Status in mdadm - Tool for managing linux software RAID arrays.:
  New
Status in “mdadm” package in Ubuntu:
  Confirmed

Bug description:
  Binary package hint: mdadm

  
  Initramfs has to start (selected) md devices in degraded mode. (The ones that contain the rootfs and swap/resume partition, if they didn't start after some time of udev hotplugging.)

  It seems to be preferable to use --incremental not only in the udev
  rules but also in the boot scripts, because is said to support "auto-
  read" mode for smoth inclusion of members that appear later on.

  But the boot script should only start selected arrays, i.e. the one
  containing the rootfs not all incomplete ones.

  So where "mdadm --run /dev/mdX" is preferable to "mdadm --assemble
  --scan" (only start selected array degraded),

  something like: "mdadm --incremental --run /dev/mdX" or to start all
  arrays in "auto-read" mode by default might be preferable to both.

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