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    SubjectRe: Linux mdadm superblock question.
    On 16/02/2010 14:37, Volker Armin Hemmann wrote:
    > On Dienstag 16 Februar 2010, John Robinson wrote:
    >> On 14/02/2010 19:13, Volker Armin Hemmann wrote:
    >>> On Sonntag 14 Februar 2010, you wrote:
    >>>> On 14/02/2010 18:40, Volker Armin Hemmann wrote:
    >>>>> On Sonntag 14 Februar 2010, you wrote:
    >>>>>> In other words, 'auto-detection' for 1.x format devices is using an
    >>>>>> initrd/initramfs.
    >>>>> which makes 1.x format useless for everybody who does not want to deal
    >>>>> with initrd/initramfs.
    >>>> True, but afaik every distro uses an initrd/initramfs and bundles tools
    >>>> making it easy to manage and customise them, so what's the problem?
    >>> and distros do it because of all the drivers they have to ship. But for
    >>> example I am not bound by such limitations. Why should I deal with that?
    >>> It is hard enough not to forget 'make modules_install'. And now add
    >>> initrd. Autodetecting just works - but if you use an initrd an it
    >>> doesn't. Where do you start?
    >>> Initrd's maybe great for distro packagers, but are they really usefull
    >>> for anybody else?
    >> Not just for distro packagers, they're useful for distro users, which
    >> are presumably 99% of Linux users these days, including the vast
    >> majority of enterprise users who like tested, supported systems.
    >> But even for people building their own kernels, initrd/initramfs are
    >> useful if you're using LVM, or indeed trying to boot off anything that's
    >> not a simple device.
    > so assume you have an initrd and metadata 1.x without auto assembling.
    > You do some changes to the raid and screw up something else. Next boot nothing
    > works. Mostly because the mdadm.conf in your initrd is not correct.
    > You whip out your trusty usb stick with a resuce system - and you are stuck.
    > If autoassembling would work, you would have working md devices you could
    > mount and edit the files you have to. But you don't and the mdadm.conf in the
    > initrd is outdated.
    > Sounds like 'you are screwed'.

    No; mdadm can assemble arrays without needing a conf file (at least
    arrays which have superblocks).

    And if you have otherwise screwed something up with the RAID, no amount
    of in-kernel autoassembly is going to help, in fact it's more likely to
    get it wrong and make things worse; you need a command line and mdadm to
    sort it out.



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