[Triumf-linux-managers] Re: Difference B/N LVM and Extended partitioning.

[Kel Raywood]

On Fri, 27 Oct 2006, Konstantin Olchanski wrote:
>... On the other hand, LVM probably prevented us from recovering the
>failed disk array on ibm00.triumf.ca ...

There was a change of metadata format from LVM1 (kernel-2.4) to LVM2
reports of corruption from LVM1 (RH-9, RHEL-3, SL-3) I have not heard of
any problems with LVM-2.  If upgrading a machine to SL-4 and you have
existing LVM1 volume-groups, then you should convert these to LVM2 using
"vgconvert".

>I find LVM more complex compared to "fdisk+mdadm" ...

The key is flexibility which often (perhaps always) leads to complexity.  
This doesn't mean it's complicated though. Also, LVM plays a different and
complimentary role.  There are situations where a combination of LVM on
top of software RAID makes sense.  You have to know what you are doing
though, and I agree that the tools are not necessarily as consistent as
they might be.

>... and I am not sure if LVM can handle common tasks, like moving disks
>between machines,

I'm not sure exactly what you mean.  It can handle without a problem,
physically taking a disk containing one a more VGs to another machine.

If you mean live migration of LVs, then it can't do this.  I believe 
that IBM's EVMS (enterprise volume-management system) can do this, and 
that it's tools are easier to use, but LVM2 was chosen for kernel 2.6 .

> ... booting from logical volumes

Correct.  You need a separate /boot parition.  The root filesystem may be 
on a LV though.

> ... and recovering from various failures.

I've not had or heard of any trouble with LVM2 corruption.

Kel