Software RAID

[Les Mikesell]

On Mon, 2006-06-26 at 10:41 -0500, Zane C.Bowers wrote:
> > > > > 
> > > > > You really do not want to do it this way. Setting up raid on a
> > > > > partitions just seems like such a bad idea on so many levels.
> > > > > You should do it on the entire disk. Last time I remember
> > > > > messing with it, the setup screen for that was not capable of
> > > > > doing that.
> > > > 
> > > > Why do you think that?
> > > > Being able to do it by partition provides for more flexibility.
> > > 
> > > Because it provides to totally freaking unneeded process. I don't
> > > see how it provides any more flexibility.
> > 
> > What if your disks aren't the same size or you want to handle
> > portions like swap in a different way?  If you do happen to
> > want identical partitioning on 2 drives you can do that in
> > one command line with sfdisk, although I prefer to do it
> > interactively to be sure it is right.
> 
> Then the smallest disk determines the size.

Or you could put the mirror of some partitions elsewhere...

> If you are not raiding the
> swap as well, you are screwed. The swap or a chunk of it going missing
> is not a good thing.

Don't count on continuing to run if one of the swap mirrors breaks.
I have a machine with a slightly flakey controller that kicks a
drive out every few months and have had it sometimes survive and
sometimes kill processes more or less at random when it loses a
swap mirror.  Since it has caused more problems to lose processes
that should be running than a clean reboot, the last time that
happened I didn't reconnect the swap mirror  - and uptime is around
500 days now (actually it shows 10 days but this is RH7.3 where the
counter wraps at 497 days and I know it didn't reboot).  Maybe things
are different in the 2.6 kernels - I have some running with mirrored
swap but none of the drives have failed there.

-- 
  Les Mikesell
   lesmikesell at gmail.com