Re: Advice on raid/lvm
On Wed, Apr 08, 2009 at 06:02:26PM -0300, Henrique de Moraes Holschuh (email@example.com) wrote:
> On Wed, 08 Apr 2009, Miles Fidelman wrote:
> > One suggestion: think very carefully about whether you really want to do
> > this.
> I second that. It is really not smart to have / (or /boot) in LVM if you
> can help it.
> I suggest that a small (1GB-4GB) partition for simple md-raid1 be used for
> / instead. That won't give you any headaches, including on disaster
> recovery scenarios.
I would respectfully disagree. There are significant advantages in
putting / in LVM, it is a well-supported, standard configuration,
and avoiding it only gives false sense of security: in a disaster
situation you need to know basics of mdadm and lvm anyway, if
you use them.
Yes, leaving / out of LVM does give you a more complete
environment to work with when system crashes in a way that LVM
(the volume group containing /) is inaccessible.
It doesn't help much though unless you also leave /usr out,
and I've lost count on how often I've enlarged /usr and
been grateful it was under LVM.
All the essential tools for managing software raid and lvm are,
however, available even without / - indeed they're in initrd,
and if you can't use them, you're out of luck anyway.
On the other hand, having / in LVM means:
* you can enlarge / when necessary;
* you can encrypt / if desired;
* you can use other RAID configurations besides RAID1 with /;
* you don't have to create separate volumes for each of
/usr, /var and /tmp (although you probably should anyway);
* it's the standard configuration, offered as automatic default
installation option, and many people are using it so finding
someone to help when needed shouldn't be hard.
As for the rest of your points, well, both software raid
and lvm do increase complexity and require learning some
new tricks, but they're well worth the trouble if you
manage any system more complex than a simple workstation,