[CentOS] LVM hatred, was Re: /boot on a separate partition?

Wed Jun 24 02:08:24 UTC 2015
Gordon Messmer <gordon.messmer at gmail.com>

On 06/23/2015 10:54 AM, Marko Vojinovic wrote:
> (1) I have no valid usecase for it. I don't remember when was the last
> time I needed to resize partitions (probably back when I was trying to
> install Windows 95). Disk space is very cheap, and if I really need to
> have *that* much data on a single partition, another drive and a few
> intelligently placed symlinks are usually enough. Cases where a symlink
> cannot do the job are indicative of a bad data structure design, and
> LVM is often not a solution, but a patch over a deeper problem
> elsewhere. Though I do admit there are some valid usecases for LVM.

Such as:
1) LVM makes MBR and GPT systems more consistent with each other, 
reducing the probability of a bug that affects only one.
2) LVM also makes RAID and non-RAID systems more consistent with each 
other, reducing the probability of a bug that affects only one.
3) MBR has silly limits on the number of partitions, that don't affect 
LVM.  Sure, GPT is better, but so long as both are supported, the best 
solution is the one that works in both cases.
4) There are lots of situations where you might want to expand a 
disk/filesystem on a server or virtual machine.  Desktops might do so 
less often, but there's no specific reason to put more engineering 
effort into making the two different.  The best solution is the one that 
works in both cases.
5) Snapshots are the only practical way to get consistent backups, and 
you should be using them.
6) If you use virtualization, LV-backed VMs are dramatically faster than 
file-backed VMs.

LVM has virtually zero cost, so there's no practical benefit to not 
using it.

When btrfs comes along and supports flexible volumes, snapshots, and 
reliable storage, then it'll make sense to ditch LVM.  Until then, LVM 
shouldn't even be a question; the answer is yes.

The point of view that LVM isn't needed when a symlink will do is no 
more valid than the opposite point of view: that there's no reason to 
play stupid games with symlinks when you have the ability to manage volumes.

> (2) It is fragile. If you have data on top of LVM spread over an array
> of disks, and one disk dies, the data on the whole array goes away.

That's true of every filesystem that doesn't use RAID or something like 
it.  It's hardly a valid criticism of LVM.

> And since hatred is an irrational thing, you need not look any
> further than that. ;-)

Well, let's not forget that you are the one who said that you despise 
LVM.  As long as you recognize that you aren't rational, I suppose we 
agree on at least one thing. :)