[Gllug] LVM & RAID

[Daniel P. Berrange]

On Sat, Mar 04, 2006 at 04:13:02AM +0000, Tethys wrote:
> 
> Mike Brodbelt writes:
> 
> >I'm about to set up a machine and would like to use both LVM and md on
> >it. The machine will have two disks, and I want them set up as a mirror
> >set, with LVM layered on top of this. I've not had cause to setup a
> >machine with both before, and there seem to be several setup options -
> >I'm curious if any of the LVM fans on the list have any specific
> >suggestions, and reasons. I tend to build by own kernels and avoid using
> >an initrd, so I'm currently tending towards keeping the root filesystem
> >outside LVM. Any particular upsides or downsides to doing this?
> 
> Nope, there's no reason to keep the root filesystem out of LVM. The
> only filesystem you need to do that with is /boot. I've had root in
> LVM on all of my machines for years now. I also have a machine running
> with ext3 on LVM on RAID1, and haven't run into any problems. It all
> Just Works(tm). I'm using an FC4 kernel. I don't know if there are any
> relevant differences between that and the Linus and/or Debian kernels.
> YMMV.

Indeed, the Fedora / RHEL default installation setup puts both root and swap
on LVM, just leaving /boot on regular partition. It 'just works'. 

> My guess would be that you'd need to keep /boot out of any RAID devices
> you create, too. Mine is. I guess it's possible that grub groks Linux
> software RAID these days, though.

I've had /boot on an MD software RAID partition before, however, its
not an entirely straightforward thing to setup - last time I checked, 
Anaconda didn't install grub in the MBR properly on MD devices, but
if you hack around with the tools, it is possible to do.

Regards,
Dan.
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