Re: [gentoo-user] RAID/LVM machine - install questions

[Florian Philipp]

Am 19.03.2010 23:40, schrieb Mark Knecht:
[...]
>
>    The LVM Install doc is pretty clear about not putting these in LVM:
>
> /etc, /lib, /mnt, /proc, /sbin, /dev, and /root
>

/boot shouldn't be there, either. Not sure about /bin

> which seems sensible. From an install point of view I'm wondering
> about RAID and how I should treat /, /boot and swap? As I'm planning
> on software RAID it seems that maybe those part of the file system
> should not even be part of RAID. Is that sensible? I always want /
> available to mount the directories above. /boot on RAID means (I
> guess) that I'd need RAID in the kernel instead of modular, and why do
> I need swap on RAID?
>[...]

If you use kernel based software RAID (mdadm, not dmraid), you can put
everything except of /boot on RAID. Even for /boot, there are
workarounds. I think there was a thread about it very recently right on
this list.

If you don't want to use an initrd (and believe me, you don't), you
cannot build the RAID components as modules, of course. But why would
you want? You need it anyway all the time between bootup and shutdown.

You don't need to put swap on a RAID. Swap has its own system for
implementing RAID-1 or RAID-0-like functionality. Using a RAID-1 for it
prevents the machine from crashing if the disk on which swap resides
dies. RAID-0 would be faster, of course.

I personally find it easier to put swap on LVM in order to make
management easier. However, if you want to use suspend-to-disk (a.k.a.
hibernate), you would need an initrd, again.

Alternatively, you can also use LVM for mirroring (RAID-1) or striping
(RAID-0) single volumes. I think this only makes sense if you just want
to protect some single volumes. After using it for some time, I found it
not worth the effort. With current disk prices, just mirror everything
and live easy ;-)

Hope this helps,
Florian Philipp