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

Luca Berra bluca at comedia.it
Thu Mar 31 07:38:17 UTC 2005

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.

>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
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.


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