Re: Resizing LVM issue

[Pascal Hambourg <pascal@plouf.fr.eu.org>]

Miroslav Skoric a écrit :
> On 06/22/2014 03:29 PM, Pascal Hambourg wrote:
> 
>> You should not have allocated all the space in the VG but instead should
>> have left some free space for further growing or creating LVs when the
>> need arises.
> 
> Let's try once again: I have not allocated anything at the time of 
> installation.

Yes you have, by accepting the installer's suggestion :

> The only thing I've done was to accept Debian installer's 
> suggestion to make the OS installation by using the whole hard disk and 
> make the LVM. (In the other words, I let the installer to calculate 
> particular partitions.)

> I see now some of you telling it should not be 
> done that way, but would not be better to blame the programmers who had 
> made such a 'bad option' within the installer?

You as the user have the final choice. You have to decide if the
installer's suggestion fits your needs and constraints. The installer
doesn't know about them.

> Secondly, either the installer and/or some online manuals had suggested 
> that the main purpose of LVM was to allow additional reallocating space 
> within the OS's partitions, later if and when needed, from within an 
> already working system.

Yes, but LVs usually contain filesystems, and as you have seen, online
shrinking of a mounted filesystem is often difficult or impossible. So
it is better to avoid this kind of situation.

If you can grow the PV (e.g. by adding a new disk) when you need to grow
a LV, then it is fine to allocate all the space of the initial PV.
However if you cannot grow the PV, then it is better to leave some of
the PV space initially unallocated and to grow LVs from that free space
when needed.