Re: (boot time consequences of) Linux mdadm superblock question.

From: martin f krafft <madduck@madduck.net>
To: Neil Brown <neilb@suse.de>
Cc: david@lang.hm, Nick Bowler <nbowler@elliptictech.com>,
	Volker Armin Hemmann <volkerarmin@googlemail.com>,
	Kyle Moffett <kyle@moffetthome.net>,
	Rudy Zijlstra <rudy@grumpydevil.homelinux.org>,
	"Mr. James W. Laferriere" <babydr@baby-dragons.com>,
	Bill Davidsen <davidsen@tmr.com>,
	Michael Evans <mjevans1983@gmail.com>,
	linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org
Subject: Re: (boot time consequences of) Linux mdadm superblock question.
Date: Thu, 18 Feb 2010 12:50:13 +1300	[thread overview]
Message-ID: <20100217235013.GB2628@lapse.rw.madduck.net> (raw)
In-Reply-To: <20100218102407.49f73d67@notabene.brown>

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also sprach Neil Brown <neilb@suse.de> [2010.02.18.1224 +1300]:
> Using user-space autodetection, you can plug "mdadm -I" into udev,
> and have arrays assembled as they are found, and filesystems
> mounted as arrays are assembled, and then you just have to wait
> for the root filesystem to appear, not for "all devices".

The mdadm experimental package offers this via debconf (default off
for now). I would appreciate testers — I literally whacked this up
on a rainy Sunday with an hangover, and while it seems to work fine,
it's probably got warts.

If you don't run Debian or a derivative, you can get the files from
debian/initramfs/* in git://git.debian.org/pkg-mdadm/mdadm.git or

  http://git.debian.org/?p=pkg-mdadm/mdadm.git;a=tree;f=debian/initramfs;hb=HEAD

don't be scared off by the complexity, incremental assembly actually
bypasses most of the (shell) code in both scripts.

> Yes, you could make the in-kernel autodetection smarter so it
> doesn't have to wait quite so long, but that would make it quite
> a bit more complex, and it is harder to maintain the complexity in
> the kernel.

It is definitely a user-space task, if you ask me.

-- 
martin | http://madduck.net/ | http://two.sentenc.es/

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