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Re: [linux-lvm] Re: putting lvm autodetect into the kernel ala md



On Wed, Mar 30, 2005 at 11:38:16PM +0800, Andy Sy wrote:
Luca Berra wrote:

>Just like the kernel is now able to autodetect and
>autoenable md RAID arrays, are there plans to make

kernel autodetection of md arrays is almost always a bad idea, it is far better to use mdadm in user space for that.

Why is this necessarily so? RAID autodetect seems to avoid a lot of configuration hassles especially when your root partition is involved. Any horror stories to tell?

yes, read the linux-raid mailing list for those, i am tired of beating the same dead horse.

>lvm do the same?  (i.e integrate the functionality
>of vgscan / vgchange -ay,-an into the kernel)

no, it is an user space task, there is no reason to
burden the kernel with this.

People have recommended against using an LVM volume for your root partition citing the hassle of a rescue disk as being the main reason. If lvm volume
this is just ridicolous fud.
in what cases you would need a rescue disk?
are those really different from the cases you'd need a rescue disk for a
normal partition-table based system.
besides, every live distro on earth now supports lvm and can be used as
a recovery tool.

autodetect and enabling were in the kernel, then
this would no longer be the case.
why?

I have a good reason for wanting my root partition
to be a logical volume: this is because I can
i have been using my root partition as a logical volume for several
years now.

Unless lvm detect/enable functionality were built into
the kernel though, you will always have to live with a physical partition holding /boot - the case today
with LVM and RAID0, but not RAID1 (from which it is
possible to boot directly off of).
i don't have a separate partition for /boot on my lvm systems.
the only reason i needed a separate boot partition was when i had a
system using raid5, so i had to have a separate raid1 partition for
booting.
Reading your arguments it appeare you are mis-informed and make a lot of
confusion between a boot loader (which is the only limitation we have in
loading a kernel/initrd/initramfs) and what the kernel can do.

Regards,
Luca

--
Luca Berra -- bluca comedia it
       Communication Media & Services S.r.l.
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