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List:       gentoo-amd64
Subject:    Re: [gentoo-amd64] conversion sda to lvm2 questions
From:       Richard Freeman <rich () gw ! thefreemanclan ! net>
Date:       2007-10-13 15:26:33
Message-ID: 4710E3A9.5050104 () thefreemanclan ! net
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Beso wrote:
>> can i use raid even if i got a single hd and a non raid board?! i think
>> i missed this thing. i knew that i could use raid on 2 separate disks of
>> the same ammount and only if i had a raid compatible board (with
>> hardware or software) but i didn't know that you could use it also on a
>> single disk.
> 

The simple answer is no - you can't use raid with one hard drive.  The
whole point of raid is to provide increased transfer rate and/or
redundancy (emphasis on the latter) by combining multiple drives together.

You do not need any special hardware to make raid work on linux (this is
software raid).  In fact, unless it is a $1000 adaptec raid controller
with battery backup that you're using I'd AVOID using any special
hardware.  My motherboard has "built-in raid support" and I don't use it
for my two raid-5 arrays or any of my raid-1s.  The cheap hardware
support provides little benefit and can cause problems (and these
solutions are almost always inflexible).

If you have only one hard drive just set up a boot partition (small), a
root partition (bigger - mine is 1GB, but you could go a little smaller
or larger), and then have one big partition assigned to lvm and then
split that up to handle everything else.

If at a later date you decide to install more hard drives and go with
raid the lvm partitions will be trivial to migrate.  Your boot will also
be easy - it isn't in use while the system is up.  The only pain will be
your root partition, and that will be mitigated by the fact that there
will be next to nothing on it.

> 
>> i tried to copy the system some time ago and found out that there are
>> files in /dev and /tmp or /var/tmp that have an enormous dimension. i
>> have left them behind and then got an unusable system for some reason.
>> the copy i had was from a livecd with the cp -p to preserve ownership
>> and permission.
>> for what i know from /dev i have only to get /dev/null and /dev/console
>> and let all others devices be created by udev. from /tmp instead i
>> should not copy anything and from /var/tmp i should copy only the
>> ccache. are my suppositions correct?
> 

If you copy files with cp - use the -a flag to make it not dereference
links/devices/etc.  "cp -a /dev/zero /tmp/zero" works just fine.

I would recommend making /tmp and /var/tmp tmpfs filesystems.  It
greatly improves performance and you shouldn't be storing anything in
these directories for longer than a reboot.  I also make myself another
tmp directory on a regular hard drive for "junk" and have tmpreaper keep
it clean - but it gets rare use.  In any case, even if you don't use
tmpfs I wouldn't bother copying them - losing your ccache isn't that big
a deal.

As somebody else pointed out, udev can take care of most of /dev, but
you do need at least a few devices there for bootup.  I don't know which
ones offhand, but you could just extract a stage 1 tarball someplace and
copy it's device directory for a core set of files.
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