Rich Freeman on 29 Sep 2013 07:41:50 -0700

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Re: [PLUG] Spanning volumes with LVM (Ubuntu)

On Sun, Sep 29, 2013 at 8:29 AM, Eric H. Johnson
<> wrote:
> I booted to the 13.04 LiveCD, ran FDisk and blew away all of the partitions
> that had been created on all of the drives. I then tried to reinstall Ubuntu
> 13.04 with LVM. It went all the way through the install, but when it got to
> installing grub it gave an error "unable to install grub - fatal error". I
> tried other locations it listed, but could not install to any of them
> either.

Ok, I can't claim to be terribly familiar with Ubuntu in particular.
I'm not sure if the automatic installer can handle multiple-volume
LVM.  You could just install to LVM on a single drive and then expand
it later though.  Expanding LVM is pretty easy when you do it right.

> I did play with encrypted LVM too, I was probably trying to tackle too much
> at once and wanted to see if I could use drive encryption across spanned
> volumes. I only managed as far as the initial drive, but that did not seem
> to be the problem with LVM. I don't need any of that for Myth, I just wanted
> to learn how to do it.

I'm sure you could manually extend with encrypted LVM, but that is
going to be a several-step process.  You'd probably want to integrate
that into whatever logic Ubuntu has for managing encrypted LVM,
because assembling all that at boot time is going to require an
initramfs, and I doubt you'll want to hand-roll that (if you were
feeling ambitious I'm sure you could do it with dracut - there might
already be a module out there which does it for you).

> Note: I was looking at RAIDing it somewhere down the line, after I get a
> third 3TB drive. There was a limit of two when I bought these, and I am
> cheap, so I was going wait for them to go on sale again to get a third one.
> :)
> For Myth, I can go ahead with how I have it installed now, and as suggested
> use the 1TB for the OS and the two 3TBs for myth media storage, unless I
> find a solution to installing grub under an LVM install.

If you're going to do that unless you really plan on having 6TB of
media anytime soon you might consider putting them in a RAID1+LVM.
You can always reshape that into a RAID5 if you get a third drive.
RAID with same-sized disks is pretty simple to set up.  If it is just
media and you don't mind the risk of losing it you could also try
btrfs (w/ built-in raid1 - you could always turn it off later since
that is easy to change under btrfs) for the media.  However, that is
somewhat risky (btrfs in raid1 mode is somewhat stable these days, but
still pretty new).  I use btrfs, but I also do a nightly rsnapshot to
ext3 of everything so I'll never be out more than a day if it all goes

> Are you saying I am still going to have a problem setting up partitions on
> the two 3TB drives with FDisk if I want them larger than 2TB? What should I
> be using instead?

Gparted with GPT partitions.  If you're not dual-booting with Windows
there really isn't much reason to use fdisk for anything these days,
though I'm not sure how the distro pre-packaged tools handle booting
off of GPT (grub certainly supports it, but that doesn't mean that
Ubuntu does).  I suspect most distros handle it though.  For non-boot
drives there are fewer issues to deal with and GPT should work with
just about everything.  I'm not sure if qtparted or other graphical
tools handle GPT - I imagine some do.

You could also just write to the raw device, but in general that isn't
the best way to do things.

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