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  1. #1

    Prevent mdadm soft-raid to mount degraded?

    Hi Community.

    I was wondering if someone knew how to set up the linux softraid 'mdadm' in a way that it would only auto-mount arrays if all disks are present.

    The default configuration is to auto-scan all partitions for raid-headers, and assemble and start any found. Even degraded.

    I could not find a hint in man or forum pages...

    The point is avoiding a resync if one disks just happens not to start properly. Also to make sure I don't miss a fault. So if a disks fails, I would notice it, solve it, and mount manually.

    I tested the default behavior:

    - disconnect on of six disks in a raid6 array.
    - start machine. It automounts degraded.
    - power off, reconnect disk.
    - start machine. It remains degraded. Disk is not
    added back into the array.
    - Add manually with --manage /dev/... --add /dev/...
    - array resyncs.

    Any help?

  2. #2
    Linux Guru Rubberman's Avatar
    Join Date
    Apr 2009
    I can be found either 40 miles west of Chicago, in Chicago, or in a galaxy far, far away.
    Well, that is the PURPOSE of RAID 5+ arrays - to allow you to continue to operate when one drive has failed (degraded mode). This allows you to replace the failed drive while still being in operation (if in a performance-degraded manner). If you don't need that capability, and are only interested in striping to get maximum performance from your drives, then you need to use a different RAID setting. The mdadm tool should allow you to do that, but remember that if one drive fails, you lose EVERYTHING...
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

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