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

Fri Jun 26 17:34:56 UTC 2015
Chris Murphy <lists at colorremedies.com>

On Fri, Jun 26, 2015 at 10:51 AM, Gordon Messmer
<gordon.messmer at gmail.com> wrote:

>> , or alternatively making the LVs
>> redundant after install is a single command (each) and you can choose
>> whether it should be mere mirroring or some MD manged RAID level (modulo
>> the LVM RAID MD monitoring issue).
> I hadn't realized that.  That's an interesting alternative to MD RAID,
> particularly for users who want LVs with different RAID levels.

LVM RAID uses the md kernel code, but is managed by LVM tools and
metadata rather than mdadm and its metadata format. It supports all
the same RAID levels these days. The gotcha is that it's obscure
enough that you won't find nearly as much documentation or help when
you arrive at DR, what to do. And anyone who lurks on the linux-raid@
list knows that a huge pile of data loss comes from users who do the
wrong thing; maybe top on the list is they for some ungodly reason
read somewhere to use mdadm -C to overwrite mdadm metadata on one of
their drives and this obliterates important information needed for
recovery and now they actually have caused a bigger problem.

At the moment, LVM RAID is only supported with conventional/thick
provisioning. So if you want to do software RAID and also use LVM thin
provisioning, you still need to use mdadm (or hardware RAID).

Chris Murphy