On Sunday 22 March 2009, Albert Hopkins wrote:
> On Sat, 2009-03-21 at 14:13 -0700, BRM wrote:
> > With all the words of LVM2 going on, I feel it is only appropriate
> > to also mention the risk.
> >
> > On a desktop I had installed LVM2 considering that I did need to
> > upgrade partitions every now and then and my previous solution was
> > add another drive/partition and cross mount - e.g. like done with
> > /usr/local under /usr, which worked fairly well. LVM2 worked great
> > - until one of the drives crashed and I was trying to figure out
> > what was on it. From that pov, volume management is a pain. I did
> > figure out what I had mounted to it - but only after deconstructing
> > the LVM configuration file to match it up with what I had put
> > there. (And no, I had not yet gotten to doing an LVM soft-RAID
> > solution to map a single LVM partition to two drives, which would
> > certainly have helped.) I got my system working by adding a new
> > drive that was not part of the volume group, and removing the old
> > drives from the volume group. Fortunately, I had my volume setup so
> > that they one partition was not made up of non-overlaping
> > partitions on different drives. (e.g. partition A = sda1 + sda2
> > instead of sda1 + sdb1.)
> >
> > So, unless you are looking to use LVM in a soft-RAID solution
> > between multiple physical drives, not multiple partitions on the
> > same drive, (e.g. partition A = sda1 + sda2, with mirror on
> > sdb1+sdb2), then I would not suggest it as should anything happen,
> > it'll make data recovery that much harder.
> >
> > Just 2 cents for the pot.
>
> With or without LVM if you lose a drive then you've lost the data on
> it. LVM does have the capability of assembling a partially damaged
> volume group just not a partially damaged logical volume which, when
> you think about it, makes sense.
>
> And you can also throw in the standard warning about backing up your
> data.
The point is that LVM adds an extra layer of complexity.
I used LVM paired with soft RAID, and when I needed to boot from a
liveCD I discovered that I had to rebuild the setup by hand.
When you're in trouble it is pristine to have a quick way out instead of
being "swamped". I had my notes and managed to reckon the configuration
(cold sweating!), but at the first occasion I reverted my system to
plain RAID.
Never used LVM for the few Gentoo server I manage.
That said backup+RAID is the way to go.
Cheers
Francesco
--
Linux Version 2.6.28-gentoo-r3, Compiled #1 SMP PREEMPT Sun Mar 8
12:38:59 CET 2009
Two 1GHz AMD Athlon 64 Processors, 4GB RAM, 4018.04 Bogomips Total
aemaeth
