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Re: Software RAID, LVM, and LILO on amd64 sarge

On Nov 7, 2005, at 3:04 AM, A J Stiles wrote:

On Saturday 05 November 2005 00:22, Thomas F. O'Connell wrote:
On Nov 4, 2005, at 5:37 PM, Thomas F. O'Connell wrote:
On Nov 4, 2005, at 4:38 PM, Gilles wrote:
During partitioning, I set up both software RAID1 and LVM. After
partitioning, I tried to install LILO in the MBR on /dev/md0, but it didn't work. I tried advanced mode and tried /dev/mapper/vg- root as
an installation target, but that was invalid, as well.

I think that you have to use an actual disk or disk partition as
At least, that's how I did it with "grub" where a disk is
specified with
something like "(hd0)" and a partition as "(hd0,0)".
To have the loader available, even if one of the disks in the array
fails, you just install it on every disks that composes "/dev/md0".

I thought I had read that grub didn't play well with sarge.

Unfortunately, now I'm struggling even to get RAID1 set up the way
I'd like, even without LVM.

Maybe this is about the methodology I'm using rather than a problem
with the installer, although I would expect the installer to be a
little more intuitive. I have a two-drive machine (two 250 GB
drives), and I'd like to configure them in a RAID1 such that each
disk is bootable.

I thought that I could just configure each disk with a single
physical RAID volume partition and then create a software RAID in
which I could create as many partitions as I want, including a /
boot partition if need be.

But I'm running into issues with seeing the remainder of the disk
space be flagged as "unusable" as soon as I create a partition in
the RAID1.

Okay. Sorry for the noise of my reply. I read this a little more


But this leaves me with my original problem.

What I'm doing now is:

1. Set up a monolithic physical volume for RAID on each disk.
2. Configure RAID1 using these volumes.
3. Configure a single LVM volume group (vg) with four logical volumes
in it: root, swap, var, and home. I don't specifically create a
volume or mount point for /boot, but I haven't gathered that that
should be necessary.

This isn't specific to 64-bit systems. Basically, a bootstrap loader such as LILO has only a very primitive filesystem; it expects the kernel to be in a
contiguous group of sectors on a single disk.  Only once the kernel is
loaded, decompressed and running do the other, more complex file systems
become available.

If you are using software RAID then you must have a /boot partition which is a non-RAID, ext3 or ext2 partition; and a separate swap partition on each drive {you don't need RAID on swap; if that goes down, the kernel's going down
anyway.  Not to mention it's a serious performance issue}.  Note, the
bootstrap loader *doesn't* care about / -- when you configure it by
running /sbin/lilo, the kernel is already running, and it will be able to find the sector where the kernel begins. So your root partition can {and
probably should} be RAID.

Build your system with a few megs ext3 / ext2 partition near the beginning, then a gig or so of swap {remember you will have 2 swap files, 1 on each drive} and then your main partitions. Once your system is installed then you will have a boot partition on sda1 but not on sdb1. So you now should copy over the contents of sda1 to sdb1 using dd. In effect you are doing RAID manually! But this only needs to be done whenever you compile a new

Well, the funny thing is that last night, as I was about to dig into manual intervention, I got the sarge amd64 installer to set things up according to my ideal, and it seems to have worked.

I'm going to verify that I can boot by either drive today, but I must've crossed my fingers just right during partitioning. In all seriousness, it's possible (read: likely) that there was a detail about one of the partitions I had attempted to setup that was configured improperly during my previous experimentation with the sarge installer.

Granted, I think it'd be wonderful if the installer eventually makes the process a little more failsafe (while preserving flexibility), but I guess that's what software development is about... :P

At the moment, though, I'm running sarge amd64 with two RAID1s, one of which is using /boot as a mount point and one of which is a physical volume for LVM, and this is just what I want.

Thomas F. O'Connell
Database Architecture and Programming
Sitening, LLC

110 30th Avenue North, Suite 6
Nashville, TN 37203-6320
615-469-5151 (fax)

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