Re: Booting - Enterprise Volume Management System

Alan Mckinnon <alan@xxxxxxxxxxxxxxxxxxx> writes:

In this case you have to explicitly specify the new size of the
filesystem in blocks. This is extremely error prone as you must know the
blocksize of your filesystem and calculate the new size based on those units. "

Until "some kernels" are identified or fixed it is not safe. I am not going to
continue pasting blocks of text from the HOWTO every time you profess ignorance.
Please read it.

So which kernels exactly are affected? Or are you getting all nervous
now because you read that there might possibly be a problem? If you
never read that howto making those claims you would not be worried, yet
it wouldn;t change the status of the bug one little bit. Think about
that.

Sheesh! I think Toby raises a reasonable concern. I would want definitive
answers about whether the problem is fixed or not in my kernel before
attempting it.

What LVM _REALLY_ does, is this:

It removes the need for a filesystem to reside on a *contiguous*
physical disk partition. You manipulate a virtual partition and don't
worry about the underlying physical disk structure

Exactly. In my case, I have a thinkpad that came with a Windows XP
partition and a 13G "Rescue and Recovery" partition. I will probably
want to completely wipe the latter and maybe I'll shrink the former
after I remove a bunch of preloaded software, maybe in steps. Then
I'll have several physical partitions that I'll want to allocate to
various existing Linux filesystems.

Of course you can also use LVM with multiple
disks, and it has a genuine advantage there. I suspect it is not as fast as
using specific software or hardware RAID though, and the HOWTO says striping
with LVM can actually reduce performance if you have more than one LV per disk.

Software raid will always be slower than LVM

Well, AFAIK LVM only does the equivalent of RAID-0. Are you claiming
that LVM striping performs better than mdraid striping? It's hard to
see why that would be so. Can you explain?

LVM has its place if you know what you are doing (and have multiple
disks with partitions which grow and never shrink), but the "LVM is
good for everybody, even laptop users" rhetoric I responded to was
OTT.

LVM really really really is good for everyone. The same way that
file systems and the journals on them are good for everyone, or a
multi-user kernel is good for everyone even if you only run as one
user at a time. It's well proven, reliable, stable, has few if any
downsides and when you need it you are very glad you've got it.

That's what I'm counting on.

--
Dave Abrahams
Boost Consulting
www.boost-consulting.com


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