LVM and RAID

[Net Llama!]

On Thu, 16 Jun 2005, Roger Oberholtzer wrote:

> On Thu, 2005-06-16 at 16:16, Mike Reinehr wrote:
> > On Thursday 16 June 2005 02:10 am, Roger Oberholtzer wrote:
> > > I have just been playing with Linux LVM and am quite impressed. It seems
> > > too simple. At least when set up from SUSE 9.2. I have a few questions
> > > for anyone who has worked with this:
> > >
> > > 1. Are there any gotchas when using a LVM on different distros? Aside
> > > from the fact that the config may be different? Anything in the LVM
> > > itself? If I set up a LVM on, say, SUSE, and later move to something
> > > else (I am not considering this - but I want to know), could I expect
> > > difficulties?
> > >
> > > 2. Can I set up a LVM that is also RAID? That is, having a file system
> > > with oodles of storage is fine, but what about failure protection?
> >
> > Roger,
> >
> > 	LVM on top of RAID works like a charm. What I have gotten from other lists,
> > and agree with, is to define three md RAID partitions:
> >
> > 	/dev/md0	RAID1	/boot	ext2	(using /dev/sda1 & /dev/sdb1)
> > 	/dev/md1	RAID1	/		ext3	(using /dev/sda2 & /dev/sdb2)
> > 	/dev/md2	RAID1	LVM PV	---		(using /dev/sda3 & /dev/sdb3)
> >
> > uses sizes you feel adequate for / & /boot & then use all the rest for md2,
> > with one VG on the single PV. Then divide up your VG with any all remaining
> > file systems (swap, /home, /var, /usr, etc.), as you please. Remember to set
> > the partition (/dev/sda... ) types as Linux RAID, so they will be
> > auto-detected at boot and don't forget to include md support & device mapper
> > support in your kernel.
>
> Wow.
>
> When I make the partition for use with LVM, I set the partition to Linux
> LVM, and tools look for these partition types when I make the VG. But if
> I build this on top of RAID, the partition will be Linux RAID instead?
>
> I need to draw a map of the layers so I can see what each one expects.
>
> But I see that I (obviously) need to get RAID working first.

I could have sworn that as far back as a yhear ago, Matt Carpenter had a
thread about the pros/cons of putting LVM on RAID and vice-versa.  You
might want to search the list archives.

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Lonni J Friedman                        netllama at linux-sxs.org
LlamaLand				http://netllama.linux-sxs.org