[K12OSN] Raid Level Choice

Les Mikesell les at futuresource.com
Wed Dec 22 19:02:50 UTC 2004

On Wed, 2004-12-22 at 10:38, Liam Marshall wrote:
> >
> and if I was considering raid for my disaster recovery option?

It is not a complete solution anyway unless you regularly
break the mirrors, take one offsite, and rebuild onto a
new replacement mirror.  RAID (1 or 5) in general lets you
survive losing one drive.  The extra benefit of RAID1 is that your
data could survive losing everything *except* one drive (i.e. server
and controller melts but you manage to salvage one drive
with data. If you are doing RAID1 in software you can plug that
drive in to any similar computer - if you are doing it in hardware
you'll probably need an exact match for the controller to read
the drive at all and if you do any other raid level you'll need
the whole drive set.

> I don't 
> really have a back up option other that a script I use to copy files 
> from the server onto my laptop's hard drive, then burning.  This of 
> course plays havoc with permissions etc. and is not a good solution, 
> just a solution.

I keep suggesting backuppc, which is a good solution and not at
all expensive if you can add a big hard drive to a desktop
pc to run it.  Since the backups run at night, this can be a PC
you already use in the daytime.

> I have a SATA raid controller that will do hardware raid.  Can you 
> explain why I might want to use LVMs instead?  I think that is what you 
> are suggesting

LVM lets you combine physical volumes so you get the same effect
as RAID0.  You should be able to do either in addition to RAID1
if you want a single volume larger than your physical partitions.
The advantge of LVM is that you can add more later and grow the
filesystem to use it, where with RAID0 you would have to completely
rebuild the layout and restore the data to change the size.

  Les Mikesell
   les at futuresource.com

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