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Re: [linux-lvm] Re: LVM2 on RAID



On Wed, Apr 27, 2005 at 03:03:47PM +0200, Måns Rullgård wrote:
/* start quote */

From: Luca Berra <bluca comedia it>
....
anyway the major issues are:
1) raid autodetect uses only the minor number stored in the superblock
to identify the array components, move a disk from a different machine
to yours and reboot it to enjoy the show

Is this really true? My kernel log has messages like these:


md: Autodetecting RAID arrays.
md: autorun ...
md: considering sdb3 ...
md:  adding sdb3 ...
md: sdb1 has different UUID to sdb3
md:  adding sda3 ...
md: sda1 has different UUID to sdb3
md: created md2

If it uses the UUID, there should be little risk of misdetection.

the issue is: if it finds the wrong one before the right one


A problem I have run into with LVM, was disks from different machines,
using the same VG names.

very true.

Can anyone conclude that passing the parameter md=0,/dev/* to kernel
parameter is a better approach than using auto detect? I don't have
a problem with having a rather long parameters in my
grub.conf/lilo.conf.

As usual, both ways have their own advantages and disadvantages. What
I like about autodetection, is that things just work, even if I
shuffle my disks for some reason.


what i did is write mdassemble to be used in initrds
it uses a mdadm.conf file where you can put the UUID and have all disk
that match a specific UUID be assembled in your MD

L.

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