Re: [gentoo-user] boot problems

[Alan McKinnon <alan.mckinnon@gmail.com>]

On 16/05/2014 13:14, covici@ccs.covici.com wrote:
> Alan McKinnon <alan.mckinnon@gmail.com> wrote:
> 
>> On 16/05/2014 12:04, Canek Peláez Valdés wrote:
>>> Whatever gets rid of LVM is good on my book. I've never understood why
>>> people uses it, and in my experience it only brings headaches.
>>> Besides, I've heard from many people that btrfs is the way to go in
>>> the future. I'm not ready to make the change yet, but I will at some
>>> point.
>>
>>
>> LVM is an excellent solution for what it was designed to do, which is to
>> deal with stuff like this:
>>
>> Oops. I misjudged how big /var/log needed to be and now I need to add
>> 50G to that partition. But it's sda6 and I have up to sda8. Arggghhhhh!
>> Now I need 5 hour downtime to play 15-pieces with fdisk.
>>
>> LVM makes that 2 commands and 12 seconds. Yes, it's a bit complex and
>> you have to hold the PV/VG/LV model in your head, but it also *fixes*
>> the issue with rigid MSDOS partition style.
>>
>> Modern filesystems like ZFS and btrfs sidestep the need for LVM in a
>> really elegant and wonderful way, none of which changes the fact that
>> ZFS/btrfs weren't around when LVM was first coded.
> 
> So is btrfs ready for production -- all the tools work, etc. to the
> level that the ext2/3/4 work?  Also, what kernel do you need for this to
> function -- and last question, how to convert an lvm volume to btrfs, or
> do you just have to make some space somewhere and copy the files?
> 
> So far, I have liked lvm, what's the advantage of btrfs over lvm?



I don't have enough experience with btrfs to answer, but I believe it's
much like ZFS in many ways. So here goes:

ZFS dispenses with the entire concept of partitions and rigidly
allocated areas of storage on a disk. All you really have is "storage".
You can divide it up into chunks and sections that look and feel like
volumes and partitions but that is not how it's implemented. You don't
create a 50G partition for logs, you tell the system to give you 50G of
space you will put logs in. And that "space" is something you can mount,
and apply permissions and quotas to.

It's a lot like having the best parts of partitions and directories in
one unit with none of the rigidity and downsides, and the whole lot is
done in a virtual manner by software.

You can drop the entire hierarchy of disk/partition/pv/vg/lv/fs right
out of your head with these new modern systems, and just not ever have
to deal with that complexity at all.

-- 
Alan McKinnon
alan.mckinnon@gmail.com