psusi at cfl.rr.com
Tue Sep 11 21:16:15 BST 2007
Kees Cook wrote:
> In Gutsy, the udev rules work for systems that have been set up
> correctly using UUIDs in their /etc/fstab. If there are
> (non-degraded) situations where LVM-on-MD does _not_ boot, it should be
> considered a bug, and a new report should be opened.
LVM-on-MD works, but is a hack. LVM on dmraid does not work ( see bug
#129285 ). The discussion for the proper fix is at:
The LVM and dmraid tools are fundamentally broken as designed with
respect to udev and need fixed to support being told what devices to
muck with by udev instead of scanning for things that look proper
devices in /dev.
The hacks that currently allows lvm on md to work are:
1) lvm explicitly refuses to scan partitions with the md type tag, which
prevents it from activating a pv directly instead of via md, which is
the problem with the above bug and why lvm on dmraid does not work.
2) For every block device add event, udev runs mdadm again to scan for
all devices it can find in /dev and probe them for md volumes and
activate any it finds which are not already active.
Instead, udev needs to identify block devices as pvs ( of an lvm or md
or dm set ), and set they belong to, then attempt to activate only that
set, directing the relevant tool to scan only those devices which have
already been identified as members of that set.
> Right, the initramfs already drops to a shell after the 3 min timeout.
> (Unless you have a buggy BIOS that causes your ACPI timer not to tick --
> have I mentioned all the crazy stuff I've banged my head against on this
> desktop?) I'd agree, 3 minutes seems too long. I think it would be safe
> to lower this to 1 minute (or even 30 seconds) since it should only be a
> timeout for the root device.
I'd like to see it do something along the lines of print a message to
the console saying not all the devices have been found after say, 15
seconds. Then they can hit a key to stop waiting and activate the set
in a degraded state, or simply continue to wait for 3 minutes.
> I like the idea of local-timeout, though I'm still generally against
> automatically bring up the degraded arrays -- however, a detailed report
> that tries to figure out what's wrong and spews help to the console would
> be nice, something like:
Having an option would be nice, but for unattended servers, they need to
not require attention if possible, so eventually it should give up
waiting and activate the set degraded.
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