LVM or not? Install Breezy

[Eric S. Johansson]

David Hart wrote:
> On Sun, 2005-10-02 at 16:32 +0900, Craig Hagerman wrote:
> 
> 
>>Good info Eric. Thanks. What if you have already installed Ubuntu
>>WITHOUT LVM, and later want it. Is is possible to changr oe things after
>>an install?
> 
> 
> Yes it's possible but depends on how you have your hard disk partitioned
> currently.
> 
> You need enough spare space to create an initial LVM partition so that
> you can copy a current partition into a logical volume created in the
> LVM.  As you free up your current partitions you can add them to the LVM
> 'pool'.

this is a great example of where the poor man's LVM comes in handy.  You 
shrink down your root and boot partitionsto something reasonably small, 
remembering of course to leave sufficient space for updates and growth. 
  Then you take the remaining space which should be "free" and install LVM
> 
> I would strongly recommend that you do this from a boot/live CD to
> ensure clean copies.
> 
> Also be very sure you have read the LVM docs carefully before trying to
> put your '/' partition in LVM; it needs special treatment as the
> bootloader can't read LVM volumes.  I myself never bother with '/' in
> LVM; if I need to set a machine to multi-boot I simply put a few small
> normal '/' partitions at the beginning of the hard disk.

this is a very good point that David raises.  Playing with breezy I 
discovered that it will support root under LVM quite nicely and 
automatically creates a boot partition of a reasonable size.  I would 
trust this (mostly) for production but, but, but don't try this trick by 
yourself without a lot of experience.  Leave root out of LVM if you are 
converting post install.  Unless of course you are looking to experience 
a royally screwed up system and reinstalling so the breezy installer can 
do things right the next time.

> Be aware, though, that if you spread your system across two disks you'll
> have approximately doubled the chance of your system becoming hosed due
> to disk failure.

Craig, here's a question you should also ask yourself.  What's your 
disaster recovery plan?  how are you going to recover if one of the 
discs in the LVM set goes out to lunch.  Here's one suggestion.  Shrink 
root as I suggested above. make a partition on the second disc the same 
size as the recently freed disk space on the first.  Then use raid one 
mirroring with LVM on top of the raid.  data redundancy and LVM to play 
with.  Then you can use the remaining space on the second disc for 
something.  Not sure what but something relatively useless like /var/log 
or /mymusic.  :-)

in theory you should be able to make both discs fully raid but raid and 
root are even more problematic than raid and LVM.

--- eric