Well, most people don't bother or even know why they would unless
jockying servers. Most will just pop in _one_ hard disk, install linux,
and call it a day celebrating the imminent death of windoze. Until it
fails, they scratch their head, cry, and get another _one_, not
understanding two redundant disks are just a possibly easy to setup/use
and would have saved the hassle.
I've been playing with raids since the 90's where slowaris taught me
partitioning strategies. I forced myself to learn/use software raid
once linux became viable for me full-time with ubuntu. Once I found the
Ubuntu Alt cd circa 6.06 had recipies for raid/lvm already, it was a
no-brainer.
I use the alt disk exclusively for desktop to layer file systems, mostly
because I :
1) need redundancy (md),
2) need crypto (luks, work laptop roams with me, or not), and
3) need versatility (lvm, partitioning extends for those "wow, win7 is
really a pig wanting 25g for a silly vm, good thing I left free space on
the vg!" moments).
You have to use that really ugly and scary ncurses menu on Alt installs,
but after dozens of installs I can fly with it much more efficiently
than the full desktop, with way more rich disk features.
I'm surprised more linux users don't pay their desktops respect they
would a server with raid. It's almost as painful to toss a disk without
redundancy in a desktop as it is a production server, in may ways more.
MDadm has been more of a pain in recent years, but all in all it's
saved me at least 3 times on personal systems over the years from a
total loss, even though recovery isn't always so straight forward. Time
well spent to learn - good subject for a hackfest.
-mb
On 03/26/2012 11:45 PM, ChasM Marshall wrote:
Wow!
This is the first I've seen here that ANYONE is using a seperate /boot
partition.
I've been using one since about 2.2 kernels.
I started out using 50Mb but, with Ubuntu and GRUB 2.0
it needs around 300Mb to 500Mb. A Fedora 15 install didn't
complain using a little as 150Mb. The minimum is for my
Windows "ntldr" which requires only 50Mb.
I've never needed LVMs or software raids for my desktop.
As I understand it, they are not involved during boot, but are
a requirement to access the newer GRUB config scripts in Ubuntu.
Use a live boot disc, as Stephen says, to be sure they are accessable.
Most of my (single-user) boxes have three to seven OSes to boot from.
All within a less than 100Gb hard drive. I'm using Grub Legacy.
If your Centos server is a large system, you may rather try this on a
seperate hardware test machine, for safety. I've seen trouble from the
Ubuntu GRUB scripts. Specifically, their "os_prober" has problems
identifying other bootable kernels and systems when generating
the new Ubuntu boot menu.
Another problem is that Ubuntu is capable of GPT or MBR hard drives.
MBR is the classic Master Boot Record.
GPT is newer, larger, and demands specific hardware abilities.
I've seen Win 7 using GPT, so caveat emptor.
(-: Chas.M. :-)
------------------------------------------------------------------------
Date: Wed, 21 Mar 2012 20:11:34 -0700
Subject: Re: Going from Centos 6 to Ubuntu Server
From: [email protected]
To: [email protected]
Well with my setup I do have the boot partition separate from the LVM
and the raid is pure software as far as I know. I was just asking if it
was safe to do so. Unfortunately the boot partition is a bit on the
smaller size at 100mb so I can easily fit around 2 kernels. I guess the
other reason I am thinking to switch is because with Ubuntu, they have a
predictable release schedule and with 12.04 LTS around the corner, I can
get a server OS that is "stable" and up to date. I know I can compile
from source all of the packages I have, like the the kernel and the
software for the LAMP stack that I am also running.
I also like the fact for the Ubuntu implementation of Samba; I can use
the the system username and password instead of first creating a user on
the system and again as a samba user. Other than that I do like Centos
right now. Thanks for your help.
On Wed, Mar 21, 2012 at 7:21 PM, Michael Butash <[email protected]
<mailto:[email protected]>> wrote:
Should be able to - depends how you're partitioned.
I'm assuming your raid0 is done with mdadm and not fake-raid based.
As long as your boot partition (non-lvm) is large enough to support
enough kernels, you should be able to install over the system lv's
you don't want, and not touch the ones that you do. Probably just
create new lv's assuming you have the space for new root, usr, var,
whatever you want. I usually create home without a separate
partition, leaving alone the existing home, and simply mount the
/home lv after reinstall "just in case".
Note I've had some weirdness with ubuntu/mdadm depending what
version mdadm metadata it was built with. In 11.04 I had to build
md's specifically to use 0.90 metadata to work fully (i.e. reboot
without having to busybox assemble md manually), 11.10 and higher I
had to build the raid specifically with the current version
(default) to work.
I layered luks/lvm/ext4 atop this too, never did figure out exactly
which was borking it, but the metadata was the trick for me. It also
could have been related to my ssd alignment partitioning that always
gave me grief with low-level fs.
-mb
On 03/21/2012 03:19 PM, Stephen wrote:
if it boots up and sees the LVM then you should be able to customer
partition and configure without reformatting.
you can look and see a fair amount without even writing changes
to the disk.
However i would still make a backup.
On Wed, Mar 21, 2012 at 1:55 PM, Nadim
Hoque<[email protected] <mailto:[email protected]>> wrote:
I currently have Centos 6 installed with software raid 0
with LVM. I was
wondering if it is possible to install Ubuntu server 10.04
with those
settings without data loss and that the current raid/lvm
will stay in tact.
So far in my experience I should be able to do this, but I
just wanted your
input on the matter. I might switch to ubuntu server for the
vast number of
packages in the default repos and when I used it before I
really liked it (I
love how the default repos have what I want, and ufw is nice
as well).
--
Nadim Hoque
Undergraduate Intern
ASU Advanced Computing Center
Cell: 480-518-6235
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Nadim Hoque
Undergraduate Intern
ASU Advanced Computing Center
Cell: 480-518-6235
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