Booting - Enterprise Volume Management System

[David Abrahams]

Alan Mckinnon <alan at linuxholdings.co.za> 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