[lug] RAID installation on Fedora 6 Zod

[Sean Reifschneider]

On Wed, May 09, 2007 at 10:42:08AM -0400, steve at badcheese.com wrote:
>I know that the Linux software raid can be a little flakey, but in my 

Flaky?  How so?  For our hosting customers doing RAID-1 on 2 discs, we
recommend doing Linux software RAID.  It's been EXTREMELY reliable for us.
Performance is great, overhead is not noticable, and tools to interact with
and manage it are fantastic.  Software RAID is pretty much the only option
that installs a tool to alert you to a drive failure as a standard part of
the OS install.

The most important part of a RAID install is, of course, making sure you
get alerted when the first drive fails.  Because you *WILL* get alerted
when the second drive fails, and you won't be happy.

And a hardware RAID controller is no guarantee of fewer bugs or more
performance.  For example, the highest end 3ware RAID cards do not
interleave RAID-10 reads across both drive pairs...  RAID 0 and 1 do not
involve any computation overhead, so offloading to hardware doesn't help as
much as RAID-5.  And there can be other more subtle problems with hardware
RAID, like not properly committing the changes to disc before removing them
from the battery backed RAM.  Read the livejournal outage report when they
lost power last year for more information about these problems.

I'd recommend you do a new install and use the RAID setup in the installer.
You can do it after the fact, but if you don't already know how to do it
I'd guess you aren't quite ready to be doing it.  As far as slapping a
hardware RAID controller, you need to know if the controller stores data on
the drive (being invasive) or not.  If it is invasive, you can't just have
it RAID the existing drive.  Again, you probably just want to do a
re-install.

Sean
-- 
 "8 out of 10 Starships that took the Folger's challenge didn't know they
 weren't using Dilithium Crystals."  -- Sean and Anne being silly one night.
Sean Reifschneider, Member of Technical Staff <jafo at tummy.com>
tummy.com, ltd. - Linux Consulting since 1995: Ask me about High Availability