[sclug] What to use LVM for

[Bob Franklin]

On Wed, 15 Mar 2006, John Stumbles wrote:

> Thinking of how to partition my new 300G hdd for my desktop I'm 
> wondering about LVM...

I recently built a server with Breezy Badger and set up LVM and MD RAID 1 
during the install; it has a pair of 300G SATA drives that I wanted in a 
RAID 1 array.


My only reason for using LVM was actually because the resulting MD from 
the RAID 1 array can't be partitioned, so the de facto solution is to turn 
it into a LVM partition and use LVM to manage this (the alternative is 
partitioning the two disks identically and creating lots of MDs for each 
one; the example had 9 and said it was 'ugly' - I had 11!).

LVM seems fairly painless and does offer the flexibility to add in extra 
storage, at a later date.  However, the use of LVM on top of MD does add a 
performance penalty of about 25%, in my simple tests (with 'bonnie').


The whole machine is set up this way (including root, /home, /usr, /tmp, 
etc) except for /boot (this is a separate MD without LVM) and swap (where 
I've just added the two partitions as distinct swap areas; since I hardly 
ever stray into swap, I've not looked into it much (I'm more concerned 
about not losing data in a crash than preventing a crash in the first 
place).

   - Bob


-- 
  Bob Franklin <r.c.franklin at reading.ac.uk>          +44 (0)118 378 7147
  Systems and Communications, IT Services, The University of Reading, UK