LVM + dmraid
David Abrahams
dave at boost-consulting.com
Mon Jul 10 17:10:40 UTC 2006
Phillip Susi <psusi at cfl.rr.com> writes:
> Could you supply some more background information?
The first piece is that I've now dropped dmraid for mdraid, since I
don't *really* need to dual boot to Windows. I want to run Windows
virtualized. Is anyone going to argue that I'm giving up something
important by using mdraid?
> What kind of raid setup do you have?
Onboard NVRaid on a Tyan Thunder K8WE s2895.
> How did you configure LVM?
Not sure I understand the question. I followed the
https://wiki.ubuntu.com/FakeRaidHowto which shows how to get dmraid
running from a LiveCD and then I just used fdisk and LVM command-line
tools to set it up.
> What kind of logical volumes did you create within the volume group?
Typical/aggressive arrangement:
/ 100M
/usr 50G
/var (also storing /tmp here) 10G
/var/spool 4G
/var/log 4G
/home 200G
/swap 16G
/usr/local 50G
/boot is on a primary partition outside LVM
> How did you direct the system to boot from the correct root volume (
> root= kernel parameter )?
The FakeRaidHowo tells all. I really did follow the directions :)
> I have not used LVM before but I have read a good deal about it, but I
> wrote the FakeRaidHowto you followed so I may be able to help.
Oh! I've spent many hours with your webpage, so thanks (I think ;->)
for writing it!
You might want to add the following:
To use LVM2 w/dmraid, change /etc/lvm/lvm.conf to include
types = [ "device-mapper", 254 ]
You'll want to do that in the chrooted filesystem also, of course, so
you do this twice, or you copy the file.
To suppress a lot of warnings about locales, install language-pack-en
immediately after chrooting.
(the 4 July dmraid restart trick works for me too)
> My initial guess is that the initrd is mounting the wrong root
> filesystem, such as your /boot ( which is a regular partition, not
> part of the volume group right? )
Right.
> and this partition has no /sys and
> /proc directories, which is why it complains about not being able to
> mount them.
Well, IIRC there was nothing useful mounted on /root. I don't
remember exactly what it was, but it just contained lost+found. I can
mount /boot on /root and I see the files.
> By the way, is there a particular reason you want to use LVM over
> dmraid? I'm not quite sure what benefits it would provide over
> conventional partitioning.
LVM has lots of benefits in terms of flexibility. It's easy to
non-destructively resize partitions, including extending them into new
disks when you run out of space. There's snapshotting and many other
useful (-sounding) features. I'm not an expert sysadmin yet, but I
don't want to cut myself from these capabilities at step 1.
--
Dave Abrahams
Boost Consulting
www.boost-consulting.com
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